MULTIPLE OPTICAL AXIS PHOTOELECTRIC SENSOR

In a multiple optical axis photoelectric sensor that stops a control output according to light being obstructed in a detection area, a first variable Con indicating a duration of optical axis scan processing for which a determination result that the detection area is in a light entrance state (light entrance detection) is obtained, and a second variable Coff indicating a duration of the optical axis scan processing for which a determination result that the detection area is in a light obstruction state (light obstruction detection) is obtained, are updated according to results of each scan in optical axis scan processing. If the value of the first variable Con, which is updated while the determination continues that the detection area is in the light entrance state, reaches a predetermined first reference value, and if a final value of the second variable Coff, which is updated according to the previous determination that the detection area is in the light obstruction state, is equal to or lower than a predetermined second reference value, a notification is made that the light obstruction is detected due to a malfunction. As a result of this notification, whether output is erroneously switched due to a cause other than an object of a detection target can correctly be made.