A motor apparatus is provided. The motor apparatus includes a motor having a rotor and a stator, an inverter used to covert an input voltage into a three-phase alternating current (AC) voltage and provide the three-phase AC voltage to the motor, an inverter controller used to control the inverter, and a rotation angle sensor. The rotation angle sensor is fixed to the motor and is used to detect a rotation angle of the motor. The inverter controller includes a calculator. The calculator calculates an offset angle of an installation position of the rotation angle sensor according to a difference between a measured value and a theoretical value of a voltage phase of the motor.