A nasal-cavity model generator (41) extracts pixels having pixel density values within a specific range from three-dimensional image data on a nasal cavity of a subject contained in DICOM data (21), and generates a nasal cavity model (50), which is a three-dimensional model of the nasal cavity, based on three-dimensional image data composed of the extracted pixels. A nasal-cavity resistance calculator (42) calculates a nasal cavity resistance (51) through fluid analysis using the nasal cavity model (50) generated by the nasal-cavity model generator (41). An adjuster (43) adjusts the specific range of the pixel density values of the pixels to be extracted for generation of the nasal cavity model (50) by the nasal-cavity model generator (41) such that the nasal cavity resistance (51) calculated by the nasal-cavity resistance calculator (42) is equal to a nasal cavity resistance (52) actually measured with a nasal-cavity draft gauge.
