In a non-isolated DC/DC converter, a reference potential for a low-side pre-driver which drives a gate of a low-side MOSFET is applied from a portion except for a main circuit passing through a high-side MOSFET and the low-side MOSFET so that a parasitic inductance between a source of the low-side MOSFET and the pre-driver is increased without increasing the sum of parasitic inductances in the main circuit and negative potential driving of the gate of the low-side MOSFET can be performed and a self turn-on phenomenon can be prevented without adding any member and changing drive system.