To provide a time counter with additional functions and its test method, which easily test both a time counter part and an additional function part in a short time.

The time counter 1 which has additional functions such as a compare function and has a multiple bit length is so constituted that a compare register part 3 constituting the additional functions and a time counter part 2 may be operated as counters of the same number of bits at the time of test. The time counter part 2 and the compare register part 3 are made to simultaneously start counting, and coincidence between both counted values is monitored, and it is discriminated that the time counter is defective when a non-coincidence occurs.