A switching control device is applied to a motor generator drive system equipped with a boost converter and an inverter. In order to avoid generation of a superimposed surge voltage, the switching control device corrects a switching timing tsw of the booster converter so that a switching timing of the booster converter is not overlapped with a switching timing of the inverter. A booster converter switching correction means corrects the switching timing tsw of the correction target to bring forward and before a start timing tpa of the switching inhibition period Pp. This makes it possible to suppress fluctuation in output of a load due to deterioration in controllability of the electric power converter, for example, suppress fluctuation in output torque of a motor generator.