PURPOSE: To provide a ramp wave generating circuit which can general plural kinds of ramp wave so that their crest value is fixed.

CONSTITUTION: An RS flip flop 32, first and second constant current sources 34 and 36 which charge and discharge a ramp wave capacitor C10, and a comparator COMP10 which compares the voltage between both ends of the ramp wave capacitor C10 with a low potential threshold VL are included. The comparator COMP12 compares the voltage between both ends of the ramp wave capacitor C10 with a central reference voltage Vcent and supplies the current of the difference to a control capacitor C12. Consequently, the voltage between its both ends has the value obtained by integrating the difference between the voltage between both ends of the ramp wave capacitor C10 and the central reference voltage Vcent, and current quantities for charging and discharging of first and second constant current sources 34 and 36 are controlled by this value. Thus, the ramp wave generating circuit which generates ramp waves having a fixed crest value is obtained.