PROBLEM TO BE SOLVED: To excellently perform similar image retrieval even between medical images which are different in image format and imaging modality.SOLUTION: In a similar image retrieval device, an image analysis section 42 analyzes an input diagnostic image and extracts an image of an attention area, and then converts the image into an image of the same dynamic range as that of a case image registered in a database 50. A feature quantity conversion section 44 calculates a feature quantity regarding a pixel value and a feature quantity regarding a shape from the image after the dynamic range conversion. A similar image retrieval section 46 performs a similar image retrieval on the basis of comparison between either or both of the calculated feature quantities and a feature quantity for retrieval registered in the database 50, and displays the result of retrieval on a display section 48. Thus, the similar image retrieval is enabled even if the dynamic range and/or the kind of imaging modality of the diagnostic image are different from those of the case image registered in the database 50.
