Abstract: A method for producing an antimicrobial agent, by cutting, or cutting and then milling a plant belonging to the family Juncaceae: mixing the cut plant with a nutrient source for a seed culture of mushroom mycelia, to form a mixture; inoculating the seed culture of mycelia to the mixture of the plant belonging to the family Juncaceae and the nutrient source and then culturing the seed culture at a growth temperature for the seed culture of mycelia to produce the antimicrobial agent.

Abstract: [Problem] To provide: an antimicrobial agent which utilizes an antimicrobial activity and a pharmacological activity of a plant belonging to the family Juncaceae, comprises a material produced by seeding a seed culture of mushroom mycelia to a plant belonging to the family Juncaceae, culturing the mycelium while adding a nutrient source to thereby proliferate the mycelium and then drying the proliferated mycelium, can exhibit an excellent antimicrobial activity even when used in a small amount, can be added to a food, can be sprayed onto an agricultural crop or soil, and can be used as a therapeutic agent for athlete's foot; and a method for producing the antimicrobial agent.