PURPOSE: To suppress the dependency of an oscillation frequency on the driving capability, etc., of an inverter which constitutes the oscillation circuit by enabling the oscillation circuit to operate with a low voltage.

CONSTITUTION: In the oscillation circuit consisting of plural inverting circuits 11, 12, and IV and plural delay circuits D1 and D2, at least one inverting circuit IV among the inverting circuits consists of plural inverters 15, 16, and 17 which are mutually connected in series. The driving capacity of the initial-stage inverter 15 which is connected right behind the input-side delay circuit D1 among those inverters 15-17 is set smaller than the driving capacity of the rear-stage inverter 17 which is connected right before the output-side delay circuit D2. Consequently, the operation of the oscillation circuit within a range of 2.7-about 5.5V is securely guaranteed and the current consumption is suppressed.