Provided is a method of manufacturing an unvulcanized tire, with which formation of air pockets is reduced in adhering a cylindrical film member and an adhesive sheet member to each other by using a forming drum having an expansion/contraction mechanism. In the method, a forming device having a forming drum (1) which has an expandable/contractible outer diameter and a forming roller (2) disposed in parallel to the forming drum (1) is used; a cylindrical film member (3) is wound around the forming drum (1) and the forming roller (2); thereafter, the diameter of the forming drum (1) is expanded whereby the cylindrical film member (3) is tensioned so as to be in close contact with the forming drum (1); and subsequently, an adhesive sheet member (4) is supplied and adhered to an outer peripheral surface of the cylindrical film member (3) on the forming roller (2), while the cylindrical film member (3) is being moved in a circumferential direction by rotating the forming drum (1).