Abstract: Provided is a linear-motion bearing, including: an outer cylinder member made of a synthetic resin, the outer cylinder member having a plurality of endless steel ball circulation paths each including an outer-peripheral-side steel ball circulation path and an inner-peripheral-side steel ball circulation path, and having sheet-like spaces in regions that are opposed to the endless steel ball circulation paths, respectively; a plurality of steel balls accommodated and arrayed in the endless steel ball circulation paths; and a synthetic resin plate, which has an arc cross section, and is fitted to each of the sheet-like spaces, the synthetic resin plate including a metal piece at a position at which the synthetic resin plate is held in contact with a steel ball row in the inner-peripheral-side steel ball circulation path, the metal piece having an elongated shape in a direction along the steel ball row in the inner-peripheral-side steel ball circulation path, in which the elongated metal piece is curved so as to