An endless circulation path for a linear rail includes a loaded path, an unloaded path and two direction change paths which are connected between the loaded path and the unloaded path. Each of the unloaded path, the direction change paths and the loaded path has top and bottom grooves. A first line is connected between top and bottom grooves of the unloaded path. A second line is connected between the top and bottom grooves of each of the direction change paths. A slope of the second line, starting from the intersection between the direction change path and the unloaded path to the intersection between the direction change path and the loaded path, is gradually inclined relative to the first line. A third line is connected between the top and bottom groove of the loaded path. The third line is inclined relative to the first line.