A vehicle having an auxiliary power source comprises a wheel drive section (4) that transmits a driving force from an electric motor via clutches (18a),(18b) capable of connecting/disconnecting the driveline to wheels (13a),(13b), an input rotation angle detecting section (17a), (17b) capable of detecting angles of an input shaft of the clutches (18a),(18b), an output rotation angle detecting section (14a),(14b) capable of detecting angles of an output shaft of the clutches (18a),(18b) and an auxiliary power output calculation section (20a),(20b) capable of calculating a difference accumulated during a predetermined time interval at which data is cleared between the input shaft angle and the output shaft angle of the clutches (18a),(18b) and of calculating auxiliary power output based on the accumulated difference between the input and the output shaft angles until the data is cleared.