An adhering detection apparatus includes a light source to emit probe light to a light translucent object during an emission period, and to stop an emission of the probe light to the light translucent object during a non-emission period, a light receiver to receive light coming from the light translucent object during the emission period and the non-emission period of the light source, and an adhering detection processor to perform an adhering detection processing for detecting a substance adhering to the light translucent object based on light quantity of the light coming from the light translucent object and received by the light receiver, and to output a detection result of the adhering detection processing. The adhering detection processor selectively performs one or more processes depending on the light quantity of the light received by the light receiver during the non-emission period of the light source.