In an ECU provided for idle-stop control, when a user start command is outputted from an ECU to start an engine in response to a manual start operation of a driver, transistors are turned on and a solenoid is operated to engage a pinion gear of a starter with a ring gear. After a delay period of a delay circuit, a transistor is turned on by an output of the delay circuit and an electromagnetic switch is turned on to energize a motor of the starter. A microcomputer measures an actual delay time from when the user start command is outputted to turn-on of the transistor and checks whether the measured time corresponds to a normal time of the delay time.