A thermal printer includes a first thermal head which is so provided as to be brought into contact with one side of a paper, a second thermal head which is so provided as to be brought into contact with the other side of the paper, and a controller. The first thermal head energizes a plurality of heater elements to print dot image data on one side of the paper. The second thermal head energizes a plurality of heater elements to print dot image data on the other side of the paper. The controller is configured to shift the energization times between the first thermal head and second thermal head.