There is disclosed an organ-adhesion preventing agent comprising a chemically-crosslinked .gamma.-polyglutamic acid as an effective ingredient, as well as a process for preventing organ from adhesion comprising a step of bringing the adhesion-preventing agent into contact with or depositing the same onto the surface of a local organ and optionally the neighborhood thereof to be prevented from the post-operative adhesion. According to the present invention, there is provided an adhesion-preventing agent which is capable of effectively preventing the surfaces of organs from adhesion, and which can be absorbed in the body with high safety and be produced with ease and has high practical usefulness, as well as a process for preventing organ from adhesion by using the adhesion-preventing agent.