A brushless resolver includes a rotor having a one-phase excitation coil and a stator having two-phase detection coils. The rotor is mounted to a shaft of a motor to detect a rotation angle of the motor. An induction coil is located around the shaft. The induction coil is connected to the excitation coil. Electromotive force induced in the induction coil by a change of magnetic flux of the motor, which passes through the shaft, is used as an excitation signal supplied to the excitation coil.