Abstract: In a head mechanism according to the present invention, a thermal head 36 is secured to a main body 20 and a platen roller 24 is mounted on the main body 20 in a freely detachable manner. The platen roller 24 is urged by a head spring 40, which is attached to the main body 20, whereby the platen roller 24 is brought into pressured contact with the thermal head 36.