1. A medical image search apparatus for searching for an image similar to a newly taken image from among medical images based on past cases, comprising: a feature calculation unit configured to calculate wavelet features of a plurality of images that have been taken and stored in the past; a keyword extraction unit configured to extract a keyword included in radiographic interpretation information for each stored image; an information storage unit configured to store the calculated wavelet features and the extracted keywords in association with the respective stored images; an image acquisition unit configured to acquire a newly taken image; a wavelet feature calculation unit configured to calculate a wavelet feature of the acquired image; a radiographic interpretation information search unit configured to extract a keyword included in radiographic interpretation information corresponding to the acquired image and, on the basis of the extracted keyword, search for similar radiographic interpretation information from the stored keywords; a spatial distance calculation unit configured to calculate a wavelet feature-based spatial distance between the acquired image and each of images corresponding to the radiographic interpretation information found; and an output unit configured to output, as a search result, any images for which the calculated wavelet feature-based spatial distance is shorter than a predetermined value, in ascending order of the calculated wavelet feature-based spatial distance.