Motor controller and construction machine provided therewith

There is provided a motor controller capable of suppressing the rotation of a motor at the time of discharging an electric accumulator, and a construction machine provided with the motor controller. A motor controller (10) is provided with a current controller (1) for controlling an electric current supplied from an electric accumulator (E) to a motor (M), and a rotation detector (2) for detecting the rotation of the motor (M). The current controller (1) supplies only a d-axis current to the motor (M) according to a discharge command. If the rotation of the motor (M) is detected by the rotation detector (2) at the time of discharging the electric accumulator (E), the current controller (1) controls the d-axis current so as to suppress the rotation of the motor (M).