To provide an operation system effectively adaptable also to an efficient thermal transfer recording device capable of changing monochromatic recording and multicolor recording by a single thermal head without the need of preparing devices for limited application for monochrome and multi-color, nor the need of a plurality of thermal heads.

Image data inputted via an interface part 201 are written in a main memory 202. The image data are taken in from the memory 202 to two or more data buffers 203, 204 successively by lines corresponding to the number of pixels of a thermal head 60. The image data taken in the data buffers 203, 204 are applied with the X-Y conversion and the parallel-serial conversion process in a first-in first-out manner so as to be sent to the thermal head 60 for executing a printing operation.