A friction disc in a tandem frictional engagement device, that is spline-fitted to a first coupling members is pressed by a first piston in a first direction, wherein the friction disc and another friction disc on the side of a first coupled member are clamped between the first piston and a first stopper member. A friction disc that is spline-fitted to a second coupling member is pressed by a second piston in an opposite direction, wherein the friction disc and another friction disc on the side of a second coupled member are clamped between the second piston and a second stopper member. A leading end of a first fitting portion of the first coupling member to which the friction disc is spline-fitted is the second stopper member and substantially abuts a second fitting portion of the second coupling member to which the friction disc is spline-fitted.