An oil pressure instruction is set by feedback control in accordance with the difference (?N) in rotary speed between an engine rotary speed (Ne) and a turbine rotary speed (Nt) so that a clutch (C1) is in standby during neutral control at an oil pressure in the vicinity of a stroke-end pressure, and the oil pressure instruction is saved. When the engine automatically stops, the saved oil pressure instruction is used to drive an electromagnetic pump (70), and a linear solenoid (SLC1) is driven by the saved oil pressure instruction. When the engine automatically starts, the clutch (C1) is completely engaged by executing apply control which drives the linear solenoid (SLC1) such that the oil pressure acting on the clutch (C1) gradually increases when rotation of the engine has stabilised after complete combustion thereof.