PURPOSE: To provide a fail safe scanning circuit wherein circuit constitution of a trouble detecting circuit is simplified and a fail safe multi-optical axis beam type sensor which uses the scanning circuit.

CONSTITUTION: A fail safe scanning circuit comprises a counting circuit 10 to periodically count the same number of clock signals CK as the number of scanning outputs generated at one full scanning period of an object to be driven and a scanning output producing circuit 20 to convert a counting output signal into a high frequency signal continued on a time base and generate the signal as a scanning output signal P1 for driving an object to be driven. Further, a fail safe trouble detecting circuit 30 is provided for announcing anbormality in a way that an output (k) of a logic value 1 equivalent to a high energy state is generated when a plurality of the scanning output signals P1 are generated, and an output (k) of a logic value 0 equivalent to a low energy state is generated when P1 is brought into an abnormal generating state on a time base and during the occurrence of a trouble of a circuit itself. A multi-optical axis beam type sensor performs drive scanning of a pair of a light emitting element and a light receiving element in synchronism with each other by using two scanning circuits.