An aspect of the invention is a printer for printing on one surface and the other surface of a sheet-like printing medium fed in a predetermined feed direction. The printer includes, a first printing part for printing on the one surface, a second printing part provided on the upstream side of the first printing part for printing on the other surface, a storage area in which first image data and second image data are stored, and an adjustment part for adjusting printing start positions of printing operations performed by the first and second printing parts by shifting the readout order of the first image data to be stored in the storage area toward the end side in accordance with a positional difference between the first printing part and the second printing part in the feed direction.