A plurality of sets of volume data, each of which represent the state of a beating heart in different phases, are obtained. Coronary artery regions are extracted from at least two sets of volume data from among the obtained sets of volume data. A plurality of analysis points are set in each extracted coronary artery region. Correlations are established among analysis points set at the same anatomical positions within the coronary artery regions. Index values that indicate the character of plaque are calculated at each analysis point within all of the coronary artery regions. The character of plaque is evaluated at positions within the coronary artery regions, by integrating the index values calculated at the analysis points corresponding to each of the positions. The evaluation results regarding the character of plaque at each of the positions within the coronary artery regions are output, correlated with information regarding the positions.