A Petri dish for cultivating bacteria used for isolating the bacteria in an enrichment culture for performing drug susceptibility tests, etc. having a mouth covered with at least one sheet and at least one small opening provided on the bottom of the Petri dish, partitions having a height equal to the distance between the bottom of the Petri dish and the sheet may be provided in the Petri dish, and a sealing lid may be fitted over the small openings. A method of inspecting drug susceptibility of bacteria which are isolated from clinical specimens etc. or purely cultured after their isolation using the Petri dish. The method using the fractionized Petri dish having a pervious sheet as the cultivation surface assorts different kinds of media from each other, the media being different in the kind of drug contained in each media or media containing the same drug but in different concentrations in each section of the Petri dish into which the bacteria is inoculated.