In a series mode, a clutch rotational speed difference ΔN is calculated, and when the clutch rotational speed difference ΔN is within a first predetermined range R1 it is determined whether a sticking determination timer t1 indicates a first predetermined time t1 or longer. When a closed sticking timer t indicates the first predetermined time t1 or longer, fuel cut is performed, and the clutch rotational speed difference ΔN is re-calculated. When the closed sticking timer t indicates a second predetermined time t2 or longer, and the clutch rotational speed difference ΔN is within a second predetermined range R2, it is determined that there is closed sticking of a clutch. When the closed sticking timer t indicates less than the time t2, and the clutch rotational speed difference ΔN is out of the second predetermined range R2, it is determined that there is no closed sticking of the clutch.