Disclosed is a hybrid system of vehicle capable of accurately generating an engine output in conformity to a required vehicle driving power and suppressing an electric power loss even when a battery is used for correcting electric power to prevent occurrence of overshoot or undershoot. The hybrid system of vehicle is designed to drive a generator by an engine and supply an electric power generated by the generator directly to a wheel-driving electric motor so as to drive the motor. The hybrid system of vehicle comprises required motor output setting means for setting a required output of the motor depending on a required vehicle driving power, required generator output setting means for setting a required output of the generator depending on the required motor output set by the required motor output setting means, and engine output setting means for setting an output of the engine depending on the required generator output set by the required generator output setting means.