To reduce a capacity of a memory in a structure that a correction value is stored by being correlated to a unit region forming a dot string and density variation is suppressed by correcting a density of each image piece according to the correction value.

This printer comprises a head for forming an image piece on a unit region; a conveyance section for conveying a medium in a conveyance direction; a memory for storing a correction value corresponding to the unit region; and a controller for forming an image piece on each unit region in a density corrected according to the correction value corresponding to the unit region by printing a print image by arranging a plurality of image pieces in the conveyance direction by performing a first printing operation, a second printing operation after the first one and a third printing operation after the second one. The memory stores the correction value corresponding to the unit region on which the image pieces are formed by the first and second printing operations, before the second printing operation (1). The memory erases the correction value corresponding to the unit region on which the image piece is formed by the first printing operation during the second printing operation, and stores the correction value corresponding to the unit region on which the image piece is formed by the third printing operation (2).