To reduce uselessness of work for taking out printing output to a desired paper size and the quantity of paper used, by reducing a state of being obliged to largely secure an upper margin by a curl of roll paper and restriction of a printing system, in an ink jet printer.

This printer has a paper residual quantity measuring means, a paper residual quantity storage means, a margin minimum value determining means determining a minimum value of a margin by a paper kind and a paper residual quantity of the roll paper and a margin control means. The margin minimum value determining means determines the minimum value of the upper margin with every combination of the paper kind and the paper residual quantity by taking into consideration the fact that the curl of the roll paper depends on the paper kind and also becomes large for approaching a core. The problem is solved by changing the minimum value of the upper margin by the paper kind and the paper residual quantity in printing.