Particles (A) including an element capable of intercalating and deintercalating lithium ions, carbon particles (B) capable of intercalating and deintercalating lithium ions, multi-walled carbon nanotubes (C), carbon nanofibers (D) and optionally electrically conductive carbon particles (E) are mixed in the presence of shear force to obtain a composite electrode material. A lithium ion secondary battery is obtained using the above composite electrode material.