A measuring tape device has a hook piece consisting of a hook plate and a pulling plate to be connected into a L-shaped structure; the edges of the hook plate are formed with an U-shaped extruded holder for holding an anti-slip piece, said pulling plate has a hollow area, a magnetic base to be screwed onto the tape is put on said pulling plate with a convex bottom portion held by said hollow area and then the magnetic base is attached to the upper surface of said pulling plate, such that said pulling plate can be moved forward and backward along the bottom surface portions surround said convex portion of said magnetic base. Besides, there is a box formed on said magnetic base for safely holding a magnetic element.