PROBLEM TO BE SOLVED: To provide a blood vessel shape measuring device that facilitates measurement.SOLUTION: A living blood vessel state measuring device comprises: a boundary point extraction unit 104 that randomly extracts multiple boundary points 126 on a boundary of a minor axis sectional shape a central coordinate estimation unit 106 that estimates a central coordinate 130 in the minor axis sectional shape on the basis of the extracted boundary points 126 and a middle position identification unit 110 that repeats, multiple times, both the extraction of the boundary points 126 and the estimation of the central coordinate 130 based on the extracted boundary points 126, and identifies a middle position 134 in the minor axis sectional shape on the basis of an average of results of the estimation of the central coordinate 130 executed multiple times. Therefore, the device can more accurately identify the middle position 134 while suppressing influence of an error by identifying the middle position 134 in the minor axis sectional shape on the basis of the results of multiple estimation executed multiple times.
