Early detection of an abnormality in a vehicle speed detection system. A continuously variable transmission (CVT) has an input shaft connected to an engine and an output shaft connected to a rear wheel. A change-gear ratio between the input and output shafts is electronically controlled. The vehicle speed detection system outputs a vehicle speed signal. An electronic control unit (ECU) detects an abnormality in the vehicle speed detection system based on at least one of a rotational speed of the engine, a rotational speed of the input shaft, and a rotational speed of the output shaft, as well as based on the vehicle speed signal outputted from the vehicle speed detection system.