An adhesion preventive kit and a method of preventing adhesion are provided which have a preventive effect on adhesion in a surrounding part of an edge of an injured or deficient tissue in guided regeneration therapy for an injured tissue. Specifically, the adhesion preventive kit includes: (A) a first membrane of at least two layers having a biodegradable base layer and an adhesion preventive layer provided respectively at outermost surfaces thereof and a second membrane of at least one layer having an adhesion preventive layer provided at an outermost surface thereof； or (B) an adhesion preventive membrane including a biodegradable base layer and an adhesion preventive layer, which membrane has an outermost surface constituted of the adhesion preventive layer and has a tissue sandwiching part.
