A detecting device is provided for detecting a transfer object. The detecting device includes a reflection type sensor mounted on a support member, an actuator which is pivoted between a first position adjacent to the sensor and a second position away from the sensor, a reflector provided at the free end of the pivotal portion of the actuator for detection by the sensor, and a stopper projection provided on the reflector for contact with the support member when the actuator is pivoted to the first position. The reflector includes a first surface and a second surface inclined relative to the first surface.