A battery-powered printer includes a printing head that has a plurality of heat generating elements arranged along a direction orthogonal to a transport direction of a recording medium and is configured to print on the recording medium, a temperature sensor configured to measure a temperature within the printer, and a processor configured to determine whether the temperature measured by the temperature sensor is equal to or lower than a predetermined threshold, determine a constant printing speed at the time of printing under a condition where the temperature is equal to or lower than the predetermined threshold, and control the printing head and a transporting speed of the recording medium so as to cause each line of the print data to be printed on the recording medium at the constant printing speed.