A printer includes a processor and a thermal head having a plurality of heating elements to print an image having a plurality of print lines on a printing medium on the basis of printing data, wherein in an initial control period, for any printing data, the processor causes the thermal head to perform a division printing for each of the print lines that are to be printed in the control period, the division printing being such that for each print line to be printed, the plurality of heating elements are divided into a plurality of subgroups and the respective subgroups of the heating elements are activated in a time-divided manner, and wherein in a normal period after the control period, the processor causes the thermal head performs a non-division printing for at least some of the print lines that are to be printed in the normal period.