PURPOSE: To ensure that a paper jam can be speedily discriminated, recording can be started and a blank part can be inexpensively reduced, by providing a rotation-detecting mechanism on a platen or on an end face of the platen to detect the rotation of the platen itself.

CONSTITUTION: A thermal head 1 is oscillatably supported on a main body, and a platen 2 is supported on the main body through a shaft so that it is driven to rotate. A recording material 3 is automatically supplied, and after the leading end thereof is passed between the head 1 and the platen 2, the head 1 is pressed against the platen 2 to clamp the recording material 3. The platen 2 is provided with a rotation-detecting disk 5 integrally on an end face thereof, and the rotation of the disk 5 is detected by a transmission-type optical sensor 6. The disk 5 is provided with slits 5a at regular angular intervals, for generating signals of the sensor 6. When the recording material 3 is jammed (a), the head 1 is pressed against the platen 2 without clamping the material 3 therebetween. Therefore, the rotation of the platen 2 is stopped due to frictional resistance between it and the head 1, and outputting of the signal from the sensor 6 is stopped, whereby the paper jam can be detected.