PURPOSE: To obtain an agar medium containing a bacterial growth supporting substance and specific amounts of a hypertonic controlling agent and animal blood, capable of detecting resistant microbe in a shortened examination time even in the presence of sensitive microbe and useful for the detection of microbe resistant to an antibacterial agent.

CONSTITUTION: Agar is heated to 50°C, incorporated with a bacterial growth supporting substance, 0.8-5% hypertonic controlling agent and 1-10% animal blood, thoroughly stirred, pipetted to a Petri dish and solidified by cooling to obtain the objective agar medium useful for the detection of microbe resistant to an antibacterial agent and the selection of an effective antibacterial agent. The medium is directly coated with an environmental material, a clinical material, an examination material for carrier, fish, shellfish, agricultural crop, processed food, etc., or with a specimen after the cell-proliferation culture and brought into contact with a single antibacterial agent, a mixture of plural antibacterial agents or a supporting material containing the antibacterial agents and a pH-buffering agent or a component to detect and develop the biochemical properties. The microbe is cultured in the above state to enable the detection of the biochemical properties characteristic to the microbe, the selection of the effective antibacterial agent and the detection of the microbe resistant to the antibacterial agent.