A thermal printer includes a thermal head, a temperature sensor, and a controller. The thermal head includes heat generation elements configured to generate heat to perform printing. The temperature sensor is disposed in the thermal printer. The controller is configured to alternately turns on and off the heat generation elements during an idle state of the thermal printer for a number of cycles with a predetermined on-time period in each cycle. The controller determines the number of cycles and the predetermined on-time period based on temperature data obtained by the temperature sensor, such that heat energy generated by the heat generation elements during each of the cycles in the idle state is lower than heat energy generated by the heat generation elements during printing of one line.