An integrated circuit includes: an inductor; a switching element connected to the inductor in series; an oscillator, of which an oscillation frequency is variable; a control unit, which controls the oscillation frequency of the oscillator based on a signal according to an output voltage of a switching power-supply device; a drive signal generating unit, which generates a drive signal used for controlling the switching element based on an output of the oscillator; a drive circuit, which drives the switching element based on the drive signal generated by the drive signal generating unit; and an on-period intermittent control unit, which intermittently performs on-period extension control in which an on-period of the switching element is set to be longer than an on-period based on the drive signal in a state where the oscillation frequency is controlled not to be fixed by the control unit.