To obtain a stable controller with a good response, by lowering its gain in a certain frequency region while leading its phase.

The positive electrode terminal of a load 5 and a ground potential point are connected by the series circuit comprising first and second resistors R1, R2 to connect a connection point (A) of the resistors R1, R2 with the inverse input terminal of an amplifier 11. An output voltage Vo is given to the inverse input terminal via the resistor R1. The inverse input terminal and the output terminal of the amplifier 11 are connected by the series circuit comprising a first capacitor C1 and third resistor R3. The positive electrode terminal of the load 5 and the ground potential point are also connected by the series circuit comprising a fourth resistor R4 and a fifth resistor R5 with a shunt capacitor C2 to connect by a sixth resistor R6 a connection point (B) of the resistors R4, R5 and the non-inverse input terminal of the amplifier 11 wherewith a command voltage Vr is connected via a seventh resistor R7. The output voltage Vo is given to the non-inverse input terminal of the amplifier 11 via the resistors R4, R6, and the command voltage Vr is given thereto via the seventh resistor R7.