This composite structure is characterized in that: an internally inserted component, which is molded from a resin material having a tensile elongation of 10% or more, is placed inside a metal member having a hollow closed cross-section such that an external load can be received by both the internally inserted component and the metal member, and the outer shape of the internally inserted component occupies 50% or more relative to the hollow closed cross-section of the metal member as projection area ratio. By disposing the resin-made internally inserted component having a specific toughness at a specified state inside the metal member having a hollow closed cross-section, especially when a collision load occurs, the metal member undergoes ductile deformation and the internally inserted component also deforms correspondingly, and thus the waveform of the load-displacement curve can approach an ideal rectangular waveform, and excellent impact energy absorbing performance can be exhibited.