A motor driving device controls braking of multiple motors each having a braking device by using a single brake power supply. The braking device includes: an electromagnetic brake that releases braking of a rotary shaft of the motor by energizing a brake coil; a conductive disk configured to rotate together with the rotary shaft and connected in series with the brake coil; and a plurality of resistors provided on a surface of the disk so as to be periodically connected in series with the brake coil as the disk rotates. The motor driving device identifies a failed braking device of the braking devices, based on the current value of the current flowing from the brake power supply and the rotational positions of the rotary shafts of the multiple motors.