A thermal printer having a thermal head with a heat element that heats a recording medium and forms a print dot by energizing the heat element generates a first energizing pulse that energizes continuously during a first period for forming a print dot when the recording medium conveyance speed is greater than a specific threshold value; and generates a second energizing pulse that alternates during the first period between energizing for a second period that is shorter than the first period and de-energizing for a third period when the recording medium conveyance speed is less than or equal to the threshold value.