A linear motion guide device includes a movable member attached onto an elongated member for forming an endless multiple-turn, helical raceway between the elongated member and the movable member and for receiving ball bearing members, and a detecting device includes a magnetic member and an integrated circuit disposed in the movable member and arranged close to the endless multiple-turn, helical raceway for detecting a moving frequency or a movement of the ball bearing members through the endless multiple-turn, helical raceway of the linear motion guide device and for detecting a wear or failure of the ball bearing members and for generating a warning signal.