The switching power supply device is provided with: a plurality of power supply circuits corresponding to phases of a multi-phase AC power supply; a switching circuit that is capable of switching a phase connected to a power supply circuit not corresponding to one discretionary phase of the multi-phase AC power supply between the one discretionary phase and a phase to which the power supply circuit corresponds; an inrush current prevention circuit for preventing inrush current that is provided on a negative-electrode-side power supply line of the multi-phase AC power supply and at a position further toward the multi-phase AC power supply than is a connection point to which each of the plurality of power supply circuits are connected; and a filter circuit that is provided between the multi-phase AC power supply and the inrush current prevention circuit and has all lines of the plurality of phases magnetically coupled thereto.