A device and method for fastening two component members. The device includes a first component member including at least two protruded portions each having a predetermined lead angle, and a second component member which keeps predetermined positional relationship with the first component member and has at least two protruded portions which are engaged with the protruded portions of the first component member, among at least two of which protruded portions, at least one of the protruded portion has a different lead angle from the lead angle of the protruded portions of the first component member, and the first and second component members can be moved closer opposite each other, the protruded portions are engaged with each other after moving opposite each other by a certain distance, and the first and second component members are integrally fixed by frictional engagement of the protruded portions differing in the lead angle.