To lessen complexity of assembling work while reducing manufacturing cost by providing a movable ribbon having a mark extending in the breadthwise direction of a ribbon and a space defined by adjacent color patches, and a single sensor for sensing the mark.

The thermal printer comprises a print head having a plurality of heating elements. A plurality of thermally activated color patches 140 are arranged continuously on a coloring matter donor ribbon 90. A space S1 includes a first mark 150 extending across the width W of the ribbon 90 and defining boundaries 155, 157 between adjacent color patches 140. The spaces S1, S2 are sufficiently transparent optically except the marks 150/160. A second mark 160 having first specified width X is spaced apart by a second specified dimension Z from the first mark 150. Combination of the first and second marks 150, 160 in the space S2 determines the head of a set of color patch 140 and the type of the ribbon 90. The mark can thereby be detected by means of a single sensor.