Abstract: Herein disclosed is a method of assembling a seat slide device which comprises a lower rail, an upper rail slidably disposed on the lower rail and rotating members disposed between the lower and upper rails. The method comprises by steps: (a) temporarily assembling the lower and upper rails; (b) disposing the rotating members between a space defined between the temporarily assembled lower and upper rails; (c) pressing the temporarily assembled lower and upper rails against each other with a given pressing force; (d) making a relative longitudinal movement between the temporarily assembled lower and upper rails with the pressing force kept applied thereto; and (e) removing the pressing force when the relative longitudinal movement counts a given number.