To obtain an object detecting apparatus which is low-cost and which prevents an object from being detected erroneously due to disturbance light, due to an electric disturbance, due to the shortage of the gain in the band width of a received light-signal amplifier circuit in the reception and amplification of modulated light or due to the shortage of a slew rate.

In an object detecting apparatus, a light receiving element which receives light generated when radiant light from a light emitting element LED(a light emitting diode) is scattered and reflected on its optical path is provided, and a received light-signal amplifier circuit which amplifies an electric signal from the light receiving element is provided. The radiant light is modulated at a predetermined frequency. In this case, a means S2, by which a light waveform by the modulation of the light emitting element LED is changed into sine waves or a waveform equivalent to sine waves or an integrated waveform, is provided.