PURPOSE: To perform printing with high reliability by shaping yokes of a magnetic attraction force generation means, i.e. a magnetic head, unsymmetrical with respect to a center line of an air gap of the magnetic head.

CONSTITUTION: Yokes forming a magnetic head are shaped asymmetrical to each other ; the tip end of a yoke 22 is made smaller in shape than the tip end of a yoke 21. In this manner, a pole 22' consisting of the yoke 22 has a magnetic flux density larger than a pole 21' consisting of the yoke 21, resulting in a large magnetic attraction force. Therefore, even if a timing of flying a magnetic ink is delayed, the magnetic ink can be flown to the pole 22' formed by the yoke 22, whereby printing with high reliability can be obtained.