To provide a more compact motor controller which is hardly affected by voltage clamp due to a constant voltage diode.

A motor controller 1 comprises: a motor path 2 for supplying power from a battery B to a motor M; a control IC4 for switching the conduction state thereof; a control IC path 3 provided in parallel with the motor path 2 and supplying power to the control IC4; a first transistor 7 which is turned on when the voltage applied to a Zener diode 6 arranged in parallel with the control IC4 reaches a clamp voltage and a current flows through the Zener diode 6; a second transistor 8 which is turned on when the first transistor 7 is turned on to feed a part of the current flowing through the control IC path 3 from an upstream position of the control IC4 toward the ground; and a capacitor 5 which eases drop of the voltage applied to the control IC4 by supplying power thereto when a current flows through the Zener diode 6 and the first and second transistors 7, 8 are turned on.