A method for detecting microorganisms, which comprises: a training step for forming, by a classifier, feature vectors based on color data on individual points within a subject region of training in a culture medium, mapping the points in the culture medium, that are specified by the feature vectors, on a high-dimensional feature space, and linearly separating a set of the points ψ (x1), that are specified by the high-dimensional feature vectors thus obtained, to thereby color-classify the class (C1) of the culture medium; and a identifying step for forming, by a classifier, feature vectors based on color data on individual inspection points within a region in the culture medium using image data obtained by capturing an image of the culture medium under cultivation, mapping the inspection points (xj), that are specified by the feature vectors, on a high-dimensional feature space, and determining whether or not the mapped points ψ (xj), that are specified by the high-dimensional feature vectors thus obtained, belong to the class (C1) of the culture medium, thereby identifying a colony based on inspection points not belonging to the class (C1) of the culture medium.