To provide a low-cost and highly durable diaphragm device for a projector which uses common two diaphragm members rotated, like double doors, in opposite directions simultaneously by electromagnetic actuators.

The diaphragm member 16 is rotatably attached to shaft members 8 and 12 via integral mediating members 20 and 21, and the diaphragm member 17 that is common to the diaphragm member 16 is rotatably attached to shaft members 9 and 13 via integral mediating members 18 and 19. The electromagnetic actuators AC1 and AC2 are attached to a plate part 1a so that output pins 33b and 25c integrated with rotors penetrate the inner surface side of the plate part 1a, and are inserted in slots formed on the mediating members 20 and 18 and slots formed on attaching pieces 16e and 17e of the diaphragm members 16 and 17, and rotate the diaphragm members 16 and 17 by rotating the rotors in the opposite directions simultaneously.