Patent ID: 7352377

Claim:
An exposure device comprising a shutter member having a slit, the shutter member being provided between a member to be scanned and a housing of a main device unit that has an optical transmission member, and being freely movable between an open position at which the slit is in opposition to the optical transmission member and a shut position at which the slit is not in opposition to the optical transmission member, a light beam being irradiated through the optical transmission member and the slit to the member to be scanned, wherein a depressed portion is provided below the slit, an aperture portion of the depressed portion being in opposition to the slit at least in a state where the shutter member is moved to the shut position at which a light path of the light beam is shut, wherein lengths of the slit in a moving direction of the shutter member and in a direction perpendicular to the moving direction are shorter than lengths of the aperture portion, and wherein a seal member is provided on the slit, a lower surface of the seal member being in contact with an entire circumference of an edge of the aperture portion in a state where the shutter member is moved to the shut position.