A diagnosis support apparatus (1) and method are provided that, when a "region in which a papillary protrusion has arisen on a surface (outermost surface) of an inner wall portion", a "region in which cells (epithelial cells) are randomly proliferating on a surface (outermost surface) of an inner wall portion", or a "region in which fibrosis is progressing" which is suspected of being a lesion part exists at an inner wall portion in a living organism having a flat surface, such as the biliary tract or pancreatic duct, automatically detect the region to support diagnosis. An arithmetic processing apparatus (90) of an OCT apparatus (1), for example, detects a position of a surface of an inner wall portion of the biliary tract or pancreatic duct by means of spatial structure data, and calculates the surface roughness based on the surface shape. A region with a high degree of surface roughness is detected as a "region in which a papillary protrusion has arisen on a surface (outermost surface) of an inner wall portion" or a "region in which cells (epithelial cells) are randomly proliferating on a surface (outermost surface) of an inner wall portion".
