An ignition device (ECU and a drive circuit) for a spark ignition type internal combustion engine that directs an ignition with generation of a predetermined start signal (i.e., falling of an ignition signal) has a circuit for monitoring generation timing of the start signal and for prohibiting the ignition based on the start signal when the start signal is generated at abnormal timing. In particular, the ignition device has a circuit for determining whether the start signal is generated at predetermined start timing and a circuit for prohibiting the ignition based on the start signal when the above circuit determines that the start signal is not generated at the start timing. Thus, damages to the engine and peripheral devices due to the ignition at the abnormal timing can be reduced.