An image processing apparatus has an image data obtaining means configured to obtain image data acquired by photographing biological tissue, a score calculating means configured to calculate a score representing severity degree of lesion of the biological tissue photographed in an image represented by the image data for each pixel based on the image data, a reliability evaluation means configured to evaluate reliability of the score based on the image data, and a score reliability calculating means configured to calculate score reliability which represents a ratio of pixels of which scores having predetermined reliability to all the pixels of the image data.
