PURPOSE: To make generative braking possible even in a high speed region by a method wherein regenerative braking is switched to generative braking by operating a filed chopper only when a regenerative load is missed during regenerative braking.

CONSTITUTION: When a regeneration mode is switched to a generation mode because of missing of a regenerative load while regenerative braking is applied to a car motor an armature chopper 10 is off and a generative braking current is produced by operating a field chopper 14 only. When the generation mode is switched to the regeneration mode the armature chopper is on again. With above method the generative braking can be applied even in the high speed region and smooth switching from the regenerative braking to the generative braking can be achieved.