Stable current control is performed even at the time of occurrence of disturbance, while the steadily occurring current pulsation is suppressed. A motor drive device 100 includes a power conversion circuit 103 that drives an alternating-current motor 101, and a controller 102 that controls the power conversion circuit 103. The controller 102 includes a voltage command calculation unit 108, a control state judgement unit 112, and a control gain change unit 113. When the determination signal output from the control state judgement unit 112 is switched from a determination signal representing a steady state to a determination signal representing a transient state, the control gain change unit 113 immediately changes the control gain to a value of normal setting, and when the judgement signal output from the control state judgement unit 112 is switched from a determination signal representing the transient state to a judgement signal representing the steady state, the control gain change unit 113 changes, with a predetermined delay time, the control gain to a value of high-gain setting.