A contour detection apparatus includes a processor. The processor learns to detect a nail contour being a detection target by setting an initial shape including feature points based on learning data each being image data on a finger including a learning target nail, and setting, as a reference point, a feature point among the feature points corresponding to a reference position, thereby obtaining contour detection information. The processor arranges, in treatment target data being image data on a finger including a treatment target nail, an initial position of the shape such that a point corresponding to the reference position in a contour of the finger including the treatment target nail is superposed on the reference point, and fits the shape to the treatment target nail from the initial position, thereby detecting the nail contour of the treatment target nail.