Abstract: A torque converter slip control device used in an automatic transmission of an internal combustion engine of a vehicle has a torque converter to transfer engine torque to an input shaft of the automatic transmission. A feed-forward slip control subroutine controls a hydraulic circuit in a feed-forward control to vary the coupling efficiency of a lockup clutch to cause the torque converter to allow slippage at a rate suitable for cancelling a fluctuation of engine torque when the internal combustion engine is at rotational speeds higher than a preselected rotational speed higher than a predetermined fuel injection recovery speed at which an injection of fuel by a fuel system is recovered during the detection of the deceleration state of the vehicle by a deceleration senser.