A challenge of the present invention is to make it possible to detect, in an intra-cavity image, a bubble area which causes deterioration in accuracy of organ determination and diseased site detection. The bubble area in the intra-cavity image can be detected properly thanks to a configuration in which an edge intensity calculator (101) detects an edge intensity of a pixel in the image, a correlation value calculator (102) calculates a correlation value between the edge intensity calculated by the edge intensity calculator (101) and a bubble model set in advance based on characteristics of a bubble image, and a bubble area detector (103) detects the bubble area in the image based on the correlation value calculated by the correlation value calculator (102).
