1. A three-dimensional model search method in which a feature value of a three-dimensional model is used to search for a similar three-dimensional model, comprising: a search object image production step of producing a plurality of two-dimensional images obtained by observing the three-dimensional model as an object of search from points of view different from one another; a first feature value extraction step of extracting the respective feature values of the two-dimensional images from the plurality of two-dimensional images produced in the search object image production step; a search key input step of inputting a two-dimensional image as a search key; a second feature value extraction step of extracting the feature value from the two-dimensional image as the search key inputted in the search key input step; and a similarity search step of using the feature values extracted in the first and second feature value extraction steps to carry out similarity search, and outputting a three-dimensional model which is similar to the search key.