A tilt adjusting method for a recording medium driving apparatus including a linear driving device including first and second parallel guide shafts. The method provides a flat mirror on a turntable, an auto-collimator, and a skew angle adjusting jig including an optically flat surface. In a first state of the jig, a height of the second end of the first shaft is adjusted so that a tilt of the first shaft in a radial direction matches a tilt of the mirror, and a height of the first end of the second shaft is adjusted so that a tilt of the first shaft in a tangential direction matches the tilt of the mirror. And, in a second state of the jig, a height of the second end of the second shaft is adjusted so that a tilt of the second shaft in a radial direction matches the tilt of the mirror.