PURPOSE: To provide the satisfactory moving state of a printing head and to keep printing quality in a satisfactory state by calculating the change of a transmission function caused by changes with the passage of time and an optimum output waveform matched with that changed transmission function.

CONSTITUTION: This method is composed of a controller 1, conveyer 2, detector 3 and identifying device 4, and the conveyer 2 is provided with a rotating part 23 to be rotated, converting means 21 for converting rotary motion to linear motion and separating means 22 for separating the rotating part 23 and the converting means 21. The controller 1 can output more than one kind of current waveforms, and the rotation of the rotating part 23 is controlled by a control part 12 corresponding to the outputted current waveform. The detector 3 detects the rotating state of the rotating part 23. The identifying device 4 detects the value of the current waveform outputted from the control part 12 at every time and the rotating state of the rotating part 23 corresponding to the current waveform by using the detector and identifies the relevant conveyer corresponding to the value of the relevant detected value at every time. Based on the identified result, the controller 1 controls the conveyer 2.