The multi-coaxial cable assembly includes a multi-coaxial cable in which a plurality of coaxial cables having insulators, external conductors, and jackets on an outer periphery of center conductors are arranged in parallel; inclined cross sections formed on the end part of the multi-coaxial cable in such a manner as exposing the center conductors and the external conductors of the coaxial cables; and a wiring board or a connector having a wiring pattern to which the center conductors and the external conductors of the coaxial cables exposed on the inclined cross sections are directly connected.