A semiconductor device includes a first timer that includes a first counter, a second timer that includes a second counter and a controller that includes a CPU in provision of a technology for efficiently diagnosing a fault of a timer that is built in the semiconductor device such as a microcontroller and so forth. The first timer performs time synchronization with the time of external equipment arranged outside the semiconductor device. The controller compares a count value of the first counter with a count value of the second counter and detects a malfunction of the second timer on the basis of a result of comparison.