The five suspects could get a month in jail on indecent exposure charges, police said.
Police were notified after the film aired on an adult cable channel in Japan and were tipped off by a viewer who recognized the Expo site from the footage.
"An actress exposed her upper body and an actor touched it inside a gondola in the one-minute scene," a police spokesperson said.
Police said the suspects, a 33-year-old television producer, a 28-year-old director, a 31-year-old cameraman, an actor, 39, and an actress, 26, intended to shoot a complete sex scene on the grounds, but decided the area was too crowded.
Names of the suspects were not released.
The cable car, called the Kikkoro Gondola, connects the northern and southern ends of the expo site.
