Abstract: A swing trainer device includes a laser beam mechanism having a laser beam light source and batteries for emitting a laser beam, and further includes a laser beam attachment member which is essentially a flexible sleeve having an open first end which is removably engaged about the end of either the handle of a golf club or the barrel of a bat, and further having an open second end which is securely engaged about the end of the back portion of the laser beam mechanism. A laser beam is directed away from and in the same plane as the handle of the golf club or the barrel of the bat. This swing trainer device is swung in a single plane to help the user maintain a consistent swing each and every time through muscle memorization.