An engine rotation information detection device including: a generator that rotates in synchronization with an engine to output an AC voltage; a pulse signal generator that detects reluctors of a rotor having many reluctors and one reluctor missing portion to generate a pulse; counting means that counts the number of detections of a zero point of a waveform of the AC voltage in each detection section, the detection section being a section between a crank angle position where the pulse signal generator detects an edge of each reluctor and a crank angle position where the pulse signal generator detects a next reluctor; and reference crank angle position identification means that specifies a detection section including the reluctor missing portion from a count value counted by the counting means and identifies a pulse generated at a reference crank angle position based on the specified detection section.