According to an embodiment, a DC-DC converter comprises: an error amplifier that receives a soft start signal and amplifies a difference between an output voltage signal and a reference voltage signal; a PWM control circuit that controls ON and OFF states of a first switching transistor and a second switching transistor based on the output of the error amplifier; a frequency divider that divides a frequency signal and outputting a divided frequency signal; an accumulator that performs an adding operation based on the divided frequency signal and a control signal; and a DA converter that generates the soft start signal based on an output of the accumulator.