A DC-DC converter includes an Nch FET1 which is series connected between an input terminal and an output terminal, and an Nch FET2 which is connected between the output terminal side of the Nch FET1 and a ground terminal. On the output terminal side of the circuits, a smoothing circuit and a comparator circuit are connected. The output side of the comparator circuit is connected to an on-time limiter circuit, and the on-time limiter circuit is connected to an H/S driver circuit for controlling the Nch FET1 through an inverter and directly connected to an L/S driver circuit for controlling the Nch FET2. Here, when a switching control signal for turning on the Nch FET1 is input to the on-time limiter circuit from the comparator, the on-time limiter circuit detects a time in the on state and outputs a signal by which the Nch FET1 is temporarily off controlled.