PURPOSE: To remove dust on a base plate by attracting and removing dust on the base plate by static electricity in an uncontacted state before a printing stage for the base plate.

CONSTITUTION: An electrostatic dust collector 10 in which dust is attracted by static electricity is provided so that it is opposed to a base plate 4 in an uncontacted state in the midway part wherein the base plate 4 is placed on a rail 2 and carried to a printing stage. An insulator 11 has been charged with necessary static electricity and the base plate 4 is passed thereunder. When dust (refuse, dirt and a foreign matter, etc.,) is stuck on the surface of the base plate 4 and the same is passed under the electrostatic dust collector 10, dust 6 on the base plate 4 is charged into polarity different from the insulator 11 by electrostatic induction and thereby attracted to the insulator 11. The passing speed of the base plate 4 at this time may be set so that the time capable of sufficiently attracting and removing dust 6 by the dust collector 10 can be secured. Thereby trouble is eliminated wherein organic substance remains and printing failure is caused.