A slider slidably straddling over a guide rail, an attachment plate having a square U-shape attached to an end surface of the slider and including opposite vertical frames and a horizontal frame connecting the vertical frames, and a sliding scraper fitted in a square U-shape groove of the attachment plate and including opposite vertical portions and a horizontal portion connecting the opposite vertical portions, and a groove portion that is in sliding contact with the guide rail are provided, and protrusion portions at which the vertical frames and the vertical portions are in abutment with each other are provided an open end portion of an inner side surface of each of the opposite vertical frames of the attachment plate or an end portion of an outer side surface of each of the opposite vertical portions of the sliding scraper, the end portion facing the relevant open end portion.