It is required to develop an adhesion preventive kit and a method of preventing adhesion, which have a preventive effect on adhesion also in a surrounding part of an edge of an injured or deficient tissue. The present invention relates to an adhesion preventive kit for preventing adhesion in guided regeneration therapy for an injured tissue. Specifically, the present invention relates to an adhesion preventive kit comprising: (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.
