1. An image search server constituting an image search system having a client computer and the image search server, comprising: at least one hardware processor configured to calculate, with regard to each image of a multiplicity of images, the values of feature quantities representing characteristics of the image, score the image based upon the calculated values of the feature quantities, and responsive to application of a first move command which moves one image among a plurality of images displayed in a candidate area, which has been formed on a display screen of said client computer, to a search result area, raise the value of feature quantities, which correspond to the feature quantities of the one image for which the first move command has been applied, and score said multiplicity of images based upon the raised values of the feature quantities.