In a PWM motor driving device, the amount of electric power supplied to a motor is controlled by controlling the ON/OFF duty factor of output transistors connected between a power source and the motor. This motor driving device has phase detecting means for detecting, among a plurality of phases of the motor, the phase which is currently being driven by the output transistors, and saturation preventing means for performing control according to the voltage of the phase detected by the phase detecting means in such a way that the output transistors are not saturated. Thus, the output transistors are controlled so as not to be saturated according to the voltage of, among the plurality of phases of the motor, the phase in which the motor is currently being driven by the output transistors. Thus, for example, when the upper output transistors are undergoing PWM switching, the lower output transistors are controlled so as not to be saturated no longer according to the voltage of the phase in which the motor is currently being driven by the upper output transistors as practiced conventionally. This helps obtain better motor rotation characteristics.