Image data of 256 gradations is converted into that of 4 gradations which can be recorded by a recording head, at a pseudo-halftone processing unit and the converted image data is supplied to a head driving unit. A control signal selector selects a control signal A from a control signal A setting unit when the image data is a natural image, and a control signal B from a control signal B setting unit when the image data is a character or a line drawing. The head driving unit generates an electric signal used to drive the recording head on the basis of gradation information from the pseudo-halftone processing unit and the control signal A or B. With this operation, when the image data is a natural image, recording is carried out with a pixel dot for image formation excellent in gradation property, and when the image data is a character or a line drawing, recording is carried out with a pixel dot for image formation which causes no jaggy or blur to be generated at hatched portions and the like.