A slip lock-up control device for a vehicle includes a torque converter having a lock-up clutch, and a slip lock-up controller. The slip lock-up controller performs slip lock-up control using a lock-up pressure difference command to match an actual slip rotational speed to a target slip rotational speed based on engine torque information indicative of input torque, when a lock-up engagement condition is fulfilled when the lock-up clutch is in a released state. During the slip lock-up control, when in an engine torque unstable range for which an engine torque has a rise gradient with respect to a rise change of an engine speed, the slip lock-up controller sets the lock-up pressure difference command to a second lock-up pressure difference command for which a pressure difference fluctuation is averaged more than a first lock-up pressure difference command used in a range other than the engine torque unstable range.