To provide a device and a method for controlling a motor capable of quickly generating a PWM signal.

The controller has a neutral-point voltage adding section 107 practicing a two-phase modulation fixing the duty ratio of one phase of an inverter 1 in 0% or 100% in a certain phase. The neutral-point voltage adding section 107 has a phase decision section 1071 deciding the maximum phase Vmax-phase and the minimum phase Vmin-phase of a voltage command value in three-phase voltage command values vu*"V", vv*"V" and vw*"V". The neutral-point voltage adding section 107 further has a comparison section 1072 comparing the absolute value |I(Vmax-phase)|"A" of the current value of the maximum phase Vmax-phase and the absolute value |I(Vmin-phase)|"A" of the current value of the minimum phase Vmin-phase. The neutral-point voltage adding section 107 further has an arithmetic section 1073 arithmetically operating a neutral-point voltage Vc on the basis of the result of the comparison of the comparison section 1072.