Abstract: Overlapped paper feed can be detected easily and promptly. Along a paper feeding path, a light emitting element 1 and a light receiving sensor 2 are placed face to face and a detection signal corresponding to the light transmissivity of paper is output. The detection signal is not amplified by one system and amplified at a predetermined amplification ratio via an amplifying circuit 3 in the other system. An A/D converter 5a or 5b is set in each system and outputs the detection signal to a CPU 6 after sampling the detection signal. The CPU 6 detects overlapped feed by selecting the system whose detection signal value is within the effective range which is not effected by noise and not at a saturation level.