Screams can be heard as he plunges headfirst toward the stage, which appears to be about 20 feet (six meters) below and reports said that he continued right into the orchestra pit, for a fall of some 30 feet.
The show is built around stunning acrobatics in which actors and stunt doubles swoop high over the stage and audience.
One New Zealander who was in the audience on Monday told CNN that he knew something was wrong when Spider-Man fell.
"The whole show, whenever they fell it was slow," he said. "This time he fell down quick, so you knew it was different."
Another audience member wrote on Twitter: "Someone took nasty fall. Screaming. 911 called. No idea what happened, kicked audience out."
A spokesman for the production suggested the actor was not badly hurt.
"An actor sustained an injury at tonight's performance,'" Rick Miramontez said.
"He fell several feet from a platform approximately seven minutes before the end of the performance, and the show was stopped. All signs were good as he was taken to the hospital for observation. We will have more news shortly."
But the accident was the fourth cast member injury in the increasingly ill-fated show, whose latest opening delay of four weeks pushed the new first night to February 7.
Blogs and online comment boards filled with calls for the show to be yanked.
"This is just getting silly. Time to shut this down," one contributor to the New York Times site said.
"Pathetic indifference to the safety and well being of actors," another said. "This show should be performed by stunt performers in Las Vegas, not on Broadway with union represented actors."
Embattled director Julie Taymor said the show's ambition meant it was never going to be easy.
"I don't think what's truly creative can be done without danger and risk," she said.
Spider-Man, born four decades ago as a Marvel comic books story, tells how geeky teenager Peter Parker develops superhero powers after being bitten by a genetically altered spider.
But the humans reprising the role are proving more vulnerable.
Natalie Mendoza, the actress playing spider goddess Arachne in the show, Tweeted: "Please pray with me for my friend Chris, my superhero who quietly inspires me everyday with his spirit."