In an engine equipped with a supercharger consisting of a compressor having a plurality of blades on a turbine shaft and a turbine, at least one index means provided on the turbine shaft or the plurality of blades, and a turbo angular velocity sensor, which detects a rotation of the index means and a rotation of the plurality of blades respectively and connected to an ECU. In the engine, also, a turbo angular velocity computing means, which calculates an angular velocity by obtaining a plurality of pulses per one rotation of the turbine shaft, is provided.