1. A printing device comprising: a thermal head that transfers overcoat ink provided on an ink sheet onto a surface of a printing paper; and a controller that causes the thermal head to perform the transfer based on pattern data, wherein the pattern data is data in which a first pattern and a second pattern are arranged alternately in a primary scanning direction and a secondary scanning direction, the first pattern includes a rectangular block of high tonal value pixels, a frame-like group of low tonal value pixels surrounding the rectangular block, of high tonal value pixels and a frame-like group of high tonal value pixels surrounding the frame-like group of low tonal value pixels, and the second pattern includes a rectangular block of low tonal value pixels, a frame-like group of high tonal value pixels surrounding the rectangular block, of low tonal value pixels and a frame like group of low tonal value pixels surrounding the group of high tonal value pixels, wherein each of the low tonal value and the high tonal value is a value that allows the overcoat ink to be transferred onto the printing paper, and the high tonal value is a value that causes glossiness of a surface of the overcoat ink to be transferred onto the printing paper, to be lower than when it is transferred by the low tonal value.