A control mechanism for a hybrid vehicle having a motor driving means enabling its running through an output of an electric motor, and an engine driving means enabling its running through an output of an engine, includes a throttle sensor and a driving change-over control unit having a mode map for determining each of working regions M, E of the motor driving unit and the engine driving unit in response to a sensing signal .theta. of the throttle sensor. The mode map is provided with a critical region Ma adjacent to the working region E of the engine driving unit in the working region M of the motor driving unit and an informing unit (display device) to inform a driver of a fact that the motor driving unit is being operated in the critical region Ma. The display device also indicates a battery residual amount.