A control section determines a driving state of a vehicle and controls first and second solenoid valves on the basis of the determined driving state. An oil passage length of a second oil discharge passage is shorter than that of a first oil discharge passage and a discharge end of the second oil discharge passage is opened at a lower position than that of the first oil discharge passage. The control section derives hydraulic oil, discharged from an oil chamber via a first shift valve, to the first oil discharge passage by means of a second shift valve when it is determined that the driving state is one during normal driving. The control section derives the hydraulic oil to the second oil discharge passage by means of the second shift valve when it is determined that the driving state is one required for rapid lock-up off.