During an operation of an engine, an input limit Swin and an output limit Swout of a battery are set to a power demand-based input limit Wp*, which depends on a power demand P*, and to an accelerator opening-based output limit Wacc, which depends on an accelerator opening Acc (steps S400 to S420). This control technique effectively prevents the battery from being frequently charged or discharged to a relatively high level of electric power within an allowable electric power range defined by the reference input limit Bwin and the reference output limit Bwout, thus restraining premature deterioration of the battery.