A ball screw device includes a screw shaft rotatably engaged with a ball nut, and a number of bearing members received between the ball nut and the screw shaft, and a circulating device for circulating the bearing members, the circulating device includes an elongate member having two end blocks for engaging into the ball nut and having a passage for receiving the bearing members, and includes a housing member and a casing member each having a portion of the passage of the elongate member for allowing the passage of the elongate member to be opened and exposed and for allowing the housing member and the casing member to be formed with molding procedures.