Disturbance noise is distinguished and an appropriate detection result is output in accordance with a state of each disturbance noise. A signal processing circuit (11) of a photodetection device (101) includes non-synchronous detection units (112, 113) that detect existence of a light reception signal which is not synchronous with a light emitting drive timing in at least one of a case where it is determined that a value of the light reception signal exceeds a predetermined first threshold and a case where the value of the light reception signal becomes less than a predetermined second threshold in a non-synchronous detection period except a synchronous detection period in a detection period in the signal processing circuit (11). In addition, is a case where existence of the light reception signal which is not synchronous with the light emitting drive timing is detected by the non-synchronous detection units (112, 113), the signal processing circuit (11) maintains a result of the detection of the existence/non-existence of the light reception signal acquired by the synchronous detection unit in a subsequent detection period.