PROBLEM TO BE SOLVED: To reduce the number of sensors and smoothly check an absolute rotational position of an engine output shaft.SOLUTION: A starter motor (rotary machine) includes an U-phase sensor SU, a V-phase sensor SV, and a W-phase sensor SW each installed in a stator at positions facing to magnets 32S and 32N, the sensors output motor control signals in accordance with polarities of the magnets 32S and 32N to be rotated, and on the basis of U-, V-, and W-phase signals (motor control signals) detected by these sensors, the starter motor (rotary machine) controls conduction of respective U-, V-, and W-coils to be rotary driven. A portion of a predetermined magnet 32S(A) is formed with a heteropolar magnetic portion 34. The U-phase sensor SU (phase sensor) is disposed on the rotational orbit 34a of the heteropolar magnetic portion 34, thereby when the U-phase sensor SU detects the heteropolar magnetic portion 34, an internal combustion engine control signal showing an absolute rotational position of a crankshaft is superposed on the motor control signal to be output.