A method for arraying head assemblies of an inkjet printer and an apparatus used for the method that can reduce a period of time taken to array the head assemblies after the head assemblies are mounted in the inkjet printer by adjusting height and rotation center of each of the head assemblies before the head assemblies are mounted in the inkjet printer, and can improve array precision of the head assemblies by adjusting a position in the X direction and a rotation angle of each of the head assemblies having already adjusted height and rotation center after the head assemblies are mounted in the inkjet printer, by adjusting a position in the Y direction of each of the head assemblies and can control an ink spray time. The method includes setting a reference height and a reference rotation center; adjusting a height and a rotation center of a head coupled to a head assembly using the reference height and the reference rotation center; mounting the head assembly in the inkjet printer; and adjusting a position of the head assembly and a rotation angle of the head assembly.