To provide a timer with self-diagnostic function.

The timer with self-diagnostic function is provided with a plurality of timer circuits each of which is provided with a counter 111 that receives a count signal and conducts counting, 1st and 2nd capture registers (112, 113) that receive a capture signal 132 and store the count of the counter 111, and a captured value mismatch detection circuit 114 that outputs a capture value mismatch detection signal when the values of the 1st and 2nd capture registers are mismatched and with a counter mismatch circuit 119 that detects whether or not counts of counters (111, 115) are matched and outputs a counter mismatch signal when mismatched. The timer with self-diagnostic function outputs a capture mismatch detection signal or the counter mismatch signal as an error detection signal so as to diagnose a defect of the timer circuit in real time.