PURPOSE: To prevent the missing of dot caused by shortage of ink in a wire, by a method wherein a thin plate ink layer forming chamber and an ink supply means are provided in an ink supply guide and the ink layer forming chamber is disposed nearly at right angles to the wire.

CONSTITUTION: With the start of printing, an armature 3 is driven by a solenoid magnet 2, whereby a wire 6 moves from a dormant position to a printing position. At this time, a step portion 6C of the wire 6 serves as a piston head; namely, it forcibly pushes out an ink, contained in a cylinder portion 7d through an ink layer forming chamber 7c, toward a printing surface out of a space between a small diameter portion 6a of the wire 6 and a guide small hole portion 7a. With the wire 6 returning to the dormant position, an ink 10A contained in the ink forming chamber 7c is sucked through an ink path 7F due to negative pressure and flows into the cylinder portion 7d. In this manner, a constant amount of ink is forcibly pushed out to the tip end portion of the wire 6, thus an ink for printing can be stably applied to a dot printing portion.