It is an object of the present invention to provide a control circuit and a control method for a current mode control type DC--DC converter capable of preventing a subharmonic oscillation even if an on-duty is not less than 50% and capable of preventing a switching frequency from fluctuating depending on an input voltage. When a high-level output signal Vo1 is inputted to a reset input terminal R of a flip-flop FF, a transistor FET1 is turned off. A phase comparator FC outputs a comparison result signal CONT in accordance with a phase difference between a delay signal FP and a reference signal FR. A delay circuit DLY outputs a high-level delay signal FP after the passage of a delay time DT adjusted in accordance with the comparison result signal CONT from the turn-off of the transistor FET1. The transistor FET1 is turned on in accordance with an input of the high-level delay signal FP.