An ECU calculates an engine speed for calculating a camshaft phase based on a time period T.theta. in which a crankshaft rotates a sampling angle .theta.. The camshaft phase is derived from a time difference between output timing of a cam angle signal and output timing of a crank angle signal based on the engine speed. According as the engine speed is lower, the sampling angle .theta. becomes small, so that the engine speed and the camshaft phase are precisely calculated.