1. A nail printing device comprising: a printing head which implements printing for a nail of a finger; a fingernail image obtaining unit which picks up an image of a region containing the nail, and obtains a nail region image from the picked-up image; a nail tip region extraction unit which extracts a nail tip region of the nail, the nail tip region not overlapping a nail bed of the finger, from the nail region image; and a shape adjustment-required region extraction unit which positionally aligns a model nail image with the nail region image, and extracts, as a shape adjustment-required region, a region located outward of an outline of the model nail image in the nail tip region.