Seat slide apparatus for vehicles

Roller receiving steps (12f) are formed in both sides of a bottom portion of a main body portion (12a) in a long lower rail (12). An upper rail (13) is formed by a main body portion (13a) and a vertical wall (13e) protruding upward from a center of an upper wall (13d) and protruding upward from an opening portion (12e). A roller (27) is inserted to a portion between the step (12f) in the bottom portion of the main body portion (12a) and the upper wall (13d) of the main body portion (13a) in the upper rail (13). Circular arc surfaces (27d) are formed in both side portions (27a) of the roller (27). The circular arc surfaces (27d) in both side portions (27a) of the roller (27) are mounted to circular arc surfaces (28) of the steps (12f).