A linear bearing is especially suitable for use when inserted into a hole in a housing and includes: a synthetic resin outer tube member, which is equipped with multiple endless steel ball circulationpaths having an outer circumferential steel ball circulation path and an inner circumferential steel ball circulation path, and is equipped with a planar space in a region facing the endless steel ball circulation paths; multiple steel balls arranged so as to be accommodated in the endless steel ball circulation paths; and a synthetic resin plate fitted into the planar space and having an arc-shaped cross section, wherein metal pieces having a slender shape along the direction of the rows of steel balls in the inner circumferential steel ball circulation path are provided at a position wherethe synthetic resin plate contacts the rows of steel balls in the inner circumferential steel ball circulation path. The slender metal pieces are curved such that the inner circumferential side protrudes in the direction along the rows of steel balls in the inner circumferential steel ball circulation path.