PURPOSE: To provide the substrate potential generation circuit capable of stably supplying the substrate potential regardless of the power supply voltage and the external environment temperature.

CONSTITUTION: The output current of a constant current source 110 consisting of a gate potential control circuit 130 and a p-channel MOSFET 118 is decided by only the sub threshold swing value of a p-channel MOSFET 114 and the resistance value of a resistance body 116. A signal out 1 which controls the operation of a ring oscillation circuit 200 is switched by the prescribed potential corresponding to the sum of the threshold value of n-channel MOSFETs 104, 106 and 108. The output current increases as the temperature rises regardless of the power supply voltage, and the prescribed potential is independent of the power supply voltage and the temperature dependance is small because the temperature characteristic of the output current value and the threshold value cancel each other. Thus, the substrate potential independent of the fluctuation of the external operation conditions can be stably controlled.