PURPOSE: To mass-produce a thermal head reduced in the irregularity of the resistance values of heating resistors and imparting high dot density.

CONSTITUTION: A glass heat accumulation layer 13 is laminated to an insulating substrate 12 and, further, lead electrodes 16 having high respectivity to infrared rays and MOD resistors 14 whose reflectivity to infrared rays is lower than that of the lead electrodes 16 are provided on said layer 13 and covered with an abrasion-resistant over-glaze layer 18 to form a thermal head 10. The over- glaze layer 18 is irradiated with infrared rays from above over the range from one lead electrodes 16 to the other lead electrodes 16 corresponding through the resistors 14 to trim the resistors 14 from the boundaries of the lead electrodes 16 and the resistors 14.