To design a constant current circuit to supply a constant current even if a deviation of a threshold voltage Vth of an FET from the set value exists on the assumption at that the fluctuation of the threshold voltage Vth of the FET has a same tendency in a circuit.

This circuit is provided with a first FET1 to drive an output current, a second FET2 and a resistor R1 which are connected in series between a power source and ground, a resistor R2 connected in series between the power source and ground, a fourth FET4, and a third FET3. The gate of the first FET1 and the gate of the third FET3 are connected to a terminal at the opposite side of ground of the resistor R1. The gate of the second FET2 is connected to the drain of the fourth FET4. A control circuit 1 is provided to correct the gate potential of the fourth FET4 for the fluctuation of the threshold voltage Vth of the FET.