The invention provides a device for bacteria classification and a pretreatment device for bacteria test. When the results of automatic classification differ from a laboratory personnel's estimation, bacterial colonies to be collected, which are displayed in an image, should be selected again one by one. Disclosed is a pretreatment device for bacteria test which comprises a means for allowing a user to instruct an increase or decrease in the classification number or the number of bacterial colonies to be displayed, and a means for displaying the classification results in accordance with the user's instruction. Thus, the results of the automatic classification can be more easily brought close to the laboratory personnel's estimation and the time required for confirming appropriate bacterial colonies to be collected can be shortened.