An automobile bodyshell frame structure includes a generally elongated first panel member, and a generally elongated second panel member having opposite side edge portions connected to the first panel member to define a hollow between the first and second panel members. A filler is disposed within a portion of a cross-section of the hollow between the first and second panel members. This filler is provided on an inner surface of one of the first and second panel members and has an average compre...

An aluminum plate and a steel plate are lapped. A rotating tool is placed on the aluminum plate, and then a pressing force and a rotational force around a pressing axis of the rotating tool are applied to the aluminum plate and the steel plate. A zinc plating layer having oxidation-prevention function is formed on the surface of the steel plate in advance. When joining the both plates, an oxidation film formed on the aluminum plate is destroyed and the zinc plating layer is pushed out outward fr...