Disclosed is an antibacterial gypsum composition for dental surgery, which eliminates pathogens transferred from the mouth of a patient, so that a dentist or others participating in dental surgery can be prevented from being infected by such pathogens during the work for dental surgery. The antibacterial gypsum composition for dental surgery comprises .alpha.-plaster for a dental model and an organic nitrogen-based compound, polyhexamethylene guanidine phosphate, as an antibacterial agent.