Safety device and malfunction detection method

Disclosed is a safety device provided with a latch circuit (124) which holds a mismatch state record when input signals from a plurality of sensors are mismatched, and releases the mismatch state record when all input signals from the plurality of sensors are OFF, and an AND circuit (123) which executes sensor malfunction determination at a timing when all the input signals from the plurality of sensors are ON, wherein the sensor malfunction determination determines that at least one of the plurality of sensors is out of order if the latch circuit (124) holds a mismatch state record, and determines that each of the plurality of sensors is not out of order if the latch circuit (124) does not hold a mismatch state record.