To avoid erroneous discrimination by a change in these relative angles in discriminating a cylinder by a crank angle signal by a crank angle sensor and a cam angle signal by a cam angle sensor.

Since a recess-projection shape of a crank rotor and a cam rotor is formed so as not to generate a different level of " H " or " L " of the cam angle signal before and after the detecting timing of a level or " H " or " L " according to a tooth defective part A and a tooth defective part B as an unequal interval part of the crank angle signal even if a VCT working angle (60 [° CA]) being a valve phase by a variable valve timing control mechanism (a relative angle changing mechanism) is changed, logic on the basis of both levels of the crank angle signal and the cam angle signal is not changed at all. Thus, since influence is not received at all even when mounting the variable valve timing control mechanism in discriminating the cylinder of an internal combustion engine, the erroneous discrimination is avoided, and quick startability is provided.