A constant current circuit includes a first current mirror composed of a first transistor formed on a first current path and a second transistor formed on a second current path, a second current mirror composed of a third transistor formed on the first current path and a fourth transistor formed on the second current path, a first diode formed on the first current path, a second diode formed on the second current path, a resistor formed on the second current path, a variable resistance element connected with the first current path and with the second current path, and a feedback unit to control a resistance value of the variable resistance element based on a current flowing through the second current path.