A control unit for a series hybrid vehicle includes a basic required output calculator for calculating a basic required output for driving the vehicle based on a vehicle speed and an accelerator pedal opening, a gradient calculator for calculating a rising gradient of a road surface on which the vehicle runs, a correction output calculator for calculating a correction output which is added to the basic required torque based on the rising gradient, and a target output calculator for calculating, when a required output which results from adding the correction output to the basic required output is larger than a predetermined value, based on the required output, a battery target electric power by which the battery is required to output part of the required output and an engine target output by which the engine is required to output the remaining of the required output.