The present invention pertains to a lock-up control device for a vehicle (engine vehicle), said lock-up control device being provided with a CVT controller unit (12) and a torque converter (4), which is disposed between an engine (1) and a continuously variable transmission (6) and has a lock-up clutch (3). When an LU engagement condition is satisfied when the lock-up clutch (3) is in a disengaged state, the CVT controller unit (12), having established an LU differential pressure instruction up to an initial differential pressure, boosts the pressure according to a ramp differential pressure produced by a predetermined slope and engages the lock-up clutch (3), the CVT controller unit (12) determines a ramp start condition for switching the LU differential pressure instruction from the initial differential pressure to the ramp differential pressure.