To miniaturize a linear motion guide system capable of easily processing.

Two rail bodies 10 and 20 which are relatively movable have raceways 13 and 23 formed by recessing two external wall surfaces 12 of a projected ridge part 11 and two internal wall surfaces 22 of a groove portion 21 facing the two external wall surfaces. A plurality of rolling bodies 32 retained by a retainer 31 are rotatably arranged on the raceways. A mesh wheel 33 meshed with a rack portion formed on the projected ridge part and a part of the groove portion in a longitudinal direction are retained by the retainer 31. Each of the two rail bodies 10 and 20 are integrally formed as one member. The rack portion is arranged on an edge portion forming a boundary between the raceways 13 and 23 and the external wall surface 12, or the internal wall surface 22. The mesh wheel 33 is rotated on a surface parallel to the external wall surface 12 and internal wall surface 22 opposed each other and is movable to a longitudinal direction.