A linear motion apparatus is comprised of: a toothed rail (40); a linearly driving mechanism section (50) having a plurality of swinging plates (53), crankshafts (54, 55), and a casing (51); and guiding means for guiding the casing (51) relatively movably with respect to the toothed rail (40). The casing (51) includes: a pair of side portions (61, 62) which are guided by the guiding means on both sides, in a tooth width direction, of the rail (40); a pair of end plate portions (63, 64) which are located on opposite sides, as viewed in a longitudinal direction of the rail (40), of the swinging plates (53) and connect opposite end portions of the pair of side plate portions (61, 62); and a coupling member (521) which is located between the plurality of crankshafts (54, 55) as viewed in the longitudinal direction of the rail and couple intermediate portions of the pair of side plate portions (61, 62). The coupling member (521) is preferably passed through the swinging plates (53). The linear motion apparatus is compact and low-cost, and capable of maintaining a stable state of meshing between swinging plates and a toothed rail even if a compact casing is adopted.