An Upper West Side businessman, after surviving a bizarre post-Halloween ax attack by a masked madman who then posed for a cellphone picture, posted his own $3,500 reward for the arrest of his assailant.

The 51-year-old victim told the Daily News he was still recovering one month after the unprovoked Nov. 1 assault by a lone attacker sporting a mask made popular by horror flick “The Purge.”

“I personally never rule my life by fear” said the victim, who hopes the money will spur someone to come forward. “You know if it’s not me, it can be somebody else.”

Between the victim and the NYPD, the reward for information leading to the axman’s arrest is $7,000. Anyone who recognizes the man is asked to call the Crime Stoppers Hotline at 800-577-TIPS.

The deranged assailant threatened to kill the victim before gashing the man’s arm and shattering his elbow while he and his girlfriend walked on Broadway near W. 61st St.

The suspect, wearing a dark-colored coat, blue jeans and black boots, fled the scene after the victim’s girlfriend snapped photos of the attacker with and without the “Purge” mask.

“I don’t like you! I’m going to kill you!” the crazed man screamed before bringing the ax down. The callous attacker, who remains a fugitive, then stopped and “literally poses for pictures,” the victim said.

The ax-wielding suspect, before fleeing underground, looked directly at the girlfriend as she snapped his photo.

“He takes off his mask and says ‘F--- the police’ as to say, ‘I don’t care, you could take my picture of my face,’” the man recalled.

The attacker also targeted the girlfriend when she tried to call cop; the woman barely dodged serious injury when he swung at her with the ax.

The gruesome encounter came after the couple spotted the man behaving strangely as they walked home from a business dinner at the restaurant Le Marais.

“Really weird, almost talking to himself type of thing, had a mask on,” he recounted. “And it wasn’t Halloween, it was the next day after Halloween. So that part was a little bit weird too. But I didn’t pay mind to it too much.”

The assailant walked calmly afterward into a nearby subway station, with eyewitnesses ignoring the screaming girlfriend’s pleas for help.

“It was disgusting,” said the boyfriend.

The horrors continued for the victim, who faces a long road to recovery and the knowledge that his attacker remains on the street. He underwent surgery at Mount Sinai Morningside, with doctors inserting screws into the bones of his shattered elbow.

And he spent the next three weeks inside his home, enduring sleepless nights as doctors warned he will most likely face pain in his joints for the rest of his life.

“I can’t sleep on the side of the injury, I feel fragile,” he said. “A lot of pain. I couldn’t shower alone for the first two weeks I’d say, or more. For example, washing your hair. I still can’t wash my hair very good because I can’t lift my arm.”

Even a month later, venturing in the crowded streets for a walk can be painful if he’s jostled by fellow pedestrians. The intensive physical therapy also exacts a heavy toll on his body, and additional surgery still looms to remove the screws and make room for bone regeneration.

The victim recalled how his attacker aimed for his head with the ax, but he was able to raise his arm in self-defense and deflect the blow. The injured man didn’t immediately know what kind of weapon the wild man was swinging.

But once the victim lifted his arm in self-defense, the blade connected with his elbow.

“You just heard this pop, like a real broken bone noise,” the victim stated.

With the suspect still at large, the victim hopes the reward incentive will speed up the process of finding the attacker.

“I’ve been living in New York for a very long time. I love New York,” he said. “When it comes to safety, it doesn’t feel safe. It went back quite a few steps than what it was and what it should be.”