PURPOSE: To equalize press contact force of a thermal head in a platen by a method wherein a bearing support material wherein a long hole determined to dimensions allowing displacement of an eccentric part in a direction almost in parallel with a contact surface of a thermal head, is formed.

CONSTITUTION: When a shaft core 12 is rotated, a shaft center of a platen shaft 2 is displaced around a center of a radius of an outer periphery of an eccentric part 13. Therefore, gaps of, both sides of the outer periphery of a platen 1 to a thermal head 5 can be varied. Then, a flexural amount is adjusted according to each strength of a plurality of compression springs energizing both sides of the thermal head 5, and pressure welding force of the thermal head 5 on both sides of the platen 1 can be equalized. In that case, though the shaft core 12 at the end part of the platen shaft 2 on the right side is displaced around the center of the radius of the outer periphery of the eccentric part 13, the eccentric part 13 can be displaced along a longitudinal direction of a long hole 21, and the core center of the platen 1 can be brought in parallel with the thermal head.