PURPOSE: To prevent the action of lock-up from being inadvertently turned on, by introducing hydraulic pressure into a direct-coupling releasing oil passage in a torque converter when valve change-over pressure is turned off, and by introducing hydraulic pressure into a direct-coupling oil passage in the torque converter when the valve change-over pressure is turned on.

CONSTITUTION: A lock-up control valve 100 is controlled by means of a solenoid valve S3. When the solenoid valve is turned off, a spool 101 is urged upward so that an oil passage L10 is communicated with a direct-coupling releasing oil passage L11, while when the solenoid valve S3 is turned on, the oil passage 10 is communicated with a direct-coupling oil passage L12. Accordingly, even through valve change-over pressure is turned off, the lock-up action may be turned off.