To provide a motor control device capable of controlling a motor by a new control system using no rotational angle sensor.

The motor is driven by a γ-shaft current Iγ in a γδ coordinate system as a virtual rotational coordinate system. The coordinate system is based on a phase-control angle θC as an angle of rotation for control is used as the γδ coordinate system. An assist torque corresponding to a difference (a load angle θL) between the phase-control angle θC and a rotor angle θM is generated. A velocity-estimation observer 43 obtains a rotor angular velocity ωn (corresponding to a rotor angular displacement per arithmetic period) at each of arithmetic periods. A rotor angular-velocity compensator 42 arithmetically operates a final rotor angular velocity ωF on the basis of the rotor angular velocity arithmetically operated by the observer 43 for estimating a velocity just before a sudden change of an indicating current value and the rotor angular velocity arithmetically operated by the observer 43 for estimating the velocity after the sudden change of the indicating current value for a fixed period when the indicating current value Iγδ* changes suddenly.