A novel antimicrobial agent which has a high degree of safety, an excellent compounding property and strong antimicrobial activity is provided. The antimicrobial agent is characterized by containing ricinoleic acid monoglyceride or diglycerine ricinoleic acid monoester as an active ingredient. The antimicrobial agent of the present invention is suitable as a compounding component of an antimicrobial object selected from a food product, a food packaging material, tableware, a perfume cosmetic, a cosmetic, an external preparation for skin, a skin washing agent, a disinfectant, a lotion for external use, an agent for hair, a wiping sterilization agent, a pharmaceutical, a quasi drug and a hygiene material for the oral cavity.
