A printing apparatus for printing on a front surface of a long printing medium, and thereafter printing on a back surface of the long printing medium, the apparatus comprising: a front surface print head for printing, by dispensing ink on the front surface of the printing medium transported in a predetermined transport direction, a cue mark indicating a printing start position in the transport direction of a front surface image, and printing the front surface image based on front surface image data with reference to the cue mark; a back surface image data corrector for creating corrected back surface image data by correcting an image size of back surface image data to be formed on the back surface of the printing medium, based on elasticity information in the transport direction after printing of the front surface image; a detector for detecting the cue mark printed on the front surface of the printing medium; and a back surface print head for printing, by dispensing ink, the corrected back surface image data on the back surface of the printing medium with reference to the cue mark detected by the detector, further comprising: a cut limiting value memory for storing beforehand a limiting value of any excess or deficiency occurring when printing is done based on the corrected back surface image data; a page interval calculator for calculating as the elasticity information a page interval in the transport direction between cue marks detected by the detector; a cut amount arithmetic processor for calculating a difference between the page interval and the image size in the transport direction of the corrected back surface image data when printing is done based on the corrected back surface image data; and an error checker for determining that an error has occurred when the difference exceeds the limiting value. a front surface print head for printing, by dispensing ink on the front surface of the printing medium transported in a predetermined transport direction, a cue mark indicating a printing start position in the transport direction of a front surface image, and printing the front surface image based on front surface image data with reference to the cue mark; a back surface image data corrector for creating corrected back surface image data by correcting an image size of back surface image data to be formed on the back surface of the printing medium, based on elasticity information in the transport direction after printing of the front surface image; a detector for detecting the cue mark printed on the front surface of the printing medium; and a back surface print head for printing, by dispensing ink, the corrected back surface image data on the back surface of the printing medium with reference to the cue mark detected by the detector, further comprising: a cut limiting value memory for storing beforehand a limiting value of any excess or deficiency occurring when printing is done based on the corrected back surface image data; a page interval calculator for calculating as the elasticity information a page interval in the transport direction between cue marks detected by the detector; a cut amount arithmetic processor for calculating a difference between the page interval and the image size in the transport direction of the corrected back surface image data when printing is done based on the corrected back surface image data; and an error checker for determining that an error has occurred when the difference exceeds the limiting value. a cut limiting value memory for storing beforehand a limiting value of any excess or deficiency occurring when printing is done based on the corrected back surface image data; a page interval calculator for calculating as the elasticity information a page interval in the transport direction between cue marks detected by the detector; a cut amount arithmetic processor for calculating a difference between the page interval and the image size in the transport direction of the corrected back surface image data when printing is done based on the corrected back surface image data; and an error checker for determining that an error has occurred when the difference exceeds the limiting value.