To provide a diaphragm device for a projector constituted so that two electromagnetic actuators arranged in a state where rotary shafts of rotors are parallel with each other rotate two diaphragm members to open outward like hinged double doors more quickly than the rotors on respective shafts parallel with rotary shafts.

The electromagnetic actuators AC1 and AC2 are attached to an outer surface of a plate part 1a, and output pins 33b and 25c of the rotors 33 and 25 penetrate to the inner surface side of the plate part 1a from circular-arc slots 1i and 1j. Shaft members 8 and 9 are erected on the inner surface of the plate part 1a between the locations of the rotary shafts 33a and 25b of the rotors 33 and 25 and an moving locus of the output pins 33b and 25c. The diaphragm members 16 and 17 having light shielding plates 16a and 17a are rotated by the output pins 33b and 25c around the shaft members 8 and 9 in opposite directions more quickly than the rotors 33 and 25.