To provide an exposure regulator simple in configuration and capable of obtaining excellent exposure even at the time of photographing when an exposing time is short.

The exposure regulator 1 is composed of a pair of sectors (1st sector 6 (and a 3rd sector 8) and a 2nd sector 7) and a pair of aperture blades (1st aperture blades 11 and a 2nd aperture blades 12). The respective aperture blades 11 and 12 are disposed at a position where they can shield both ends in the longitudinal direction of an aperture formed by the respective sectors 6 to 8 when an exposure aperture part 20 is transited from an opened state to a closed state from light.