Embodiments provide a helical layer structure including: a helical core member which is formed of a flexible, lengthy, flat plate-like core member and which is formed of a steel plate made of a metal material, such as iron; and a polymeric coating layer which is formed of a polymeric material such as a thermosetting elastic material or a thermoplastic elastic material, and which coats the helical core member. The manufacturing method of the helical layer structure includes: a feeding step of feeding a core member having flexibility; a supply step of supplying the polymeric material having fluidity; a coating step of coating the core member with the polymeric material; a cooling step of cooling a coated intermediate which is coated with the polymeric material; and a helix formation step of helically twisting the coated intermediate to form the helical layer structure.

A composite member includes a metal sheet having a bent portion formed by bending, and a resin member joined to at least a part of the bent portion. The metal sheet includes an opening provided on an inner side of the bent portion, and a tapered recess that tapers off from an outer side of the bent portion toward the opening. The resin member includes an inner resin part filled in the recess, and an exposed resin part provided to be continuous with the inner resin part and to extend to an inner surface of the bent portion through an edge portion of the opening.

Embodiments provide a helical layer structure including: a helical core member which is formed of a flexible, lengthy, flat plate-like core member and which is formed of a steel plate made of a metal material, such as iron; and a polymeric coating layer which is formed of a polymeric material such as a thermosetting elastic material or a thermoplastic elastic material, and which coats the helical core member. The manufacturing method of the helical layer structure includes: a feeding step of feeding a core member having flexibility; a supply step of supplying the polymeric material having fluidity; a coating step of coating the core member with the polymeric material; a cooling step of cooling a coated intermediate which is coated with the polymeric material; and a helix formation step of helically twisting the coated intermediate to form the helical layer structure.