An inkjet printer with a frame and a printhead module further includes an adjusting piece and a pair of adjusting units, for adjusting a distance between the printhead module and a printing medium. An indicating portion and a scale portion are further disposed on the adjusting unit to indicate up-and-down moving amplitude of the adjusting piece. Thereby, the up-and-down moving amplitude of the printhead module is quantized, and the adjustment of the distance between the printhead module and the printing medium is precisely controlled.