A control target value calculation portion (42) calculates a control target value for an engine (32) based on a control instruction amount requested by a driver, which is calculated by a driver's instruction amount calculation portion (14), and control instruction amounts requested by control units such as a driver support amount calculation portion (16) and a wheel stability control amount calculation portion (18). A horsepower conversion portion (44) converts the control target value into a control target horsepower. Meanwhile, an allowable horsepower range calculation portion (40) calculates a target instruction horsepower and an allowable horsepower range based on the information from the driver's instruction amount calculation portion (14). Even when an integrated-control involving multiple control units is performed, a monitor portion (46) determines whether the control target derived through conversion is within the allowable horsepower range. Thus, whether the control target is within the allowable horsepower range is easily and accurately determined, and control of a drive source of a vehicle is monitored.