A surgery assistance apparatus includes an organ region extraction unit that extracts a tubular organ region from a three-dimensional image obtained by imaging a tubular organ and a blood vessel dominating the tubular organ, a region-of-interest setting unit that sets a region of interest in the tubular organ region, a blood vessel region extraction unit that extracts a blood vessel region dominating the tubular organ from the three-dimensional image, a branching structure extraction unit that extracts a branching structure of the blood vessel from the blood vessel region, and a dominating blood vessel identification unit that identifies a dominating blood vessel region in the blood vessel region that dominates the region of interest by using a positional relationship between a terminal end point of the extracted branching structure and the set region of interest.
