An ECU calculates peak-current arrival time (time elapsed before a detected current arrives at a target peak current), and calculates predetermined-current arrival difference time (time elapsed before the detected current becomes lower than a predetermined current after exceeding the predetermined current). The ECU uses a beforehand stored relationship between the predetermined-current arrival difference time and defined peak-current arrival time to calculate the defined peak-current arrival time corresponding to the latest predetermined-current arrival difference time. The ECU uses such defined peak-current arrival time to compare the latest peak-current arrival time with the defined peak-current arrival time (for example, calculates a difference between the peak-current arrival time and the defined peak-current arrival time), and thus determines a shift in detected current of a current detection circuit.