Philan-Tam-Duy Le of Julian, which is about 60 miles northeast of San Diego, was arrested just after 3 p.m. when police observed the truck carrying the guillotine was illegally parked east of the Capitol grounds, police said.
Photos released by Capitol Police showed a large guillotine in the bed of the pickup truck.
Police said the suspect had driven from California to Washington, D.C., but investigators are still working to determine why he made the trip.
The suspect was arrested on suspicion of carrying a dangerous weapon.
A guillotine is an instrument for administering capital punishment by beheading and consists of a heavy blade mounted on a tall wooden frame. It was invented in late-18th Century France and became a symbol of the Reign of Terror during the French Revolution.
The Associated Press contributed to this report.