An apparatus for orbital angular momentum (OAM) mode combination and an antenna apparatus for multi-mode generation are provided. The apparatus for OAM mode combination includes three input ports configured to receive independent OAM mode signals, four output ports configured to output OAM mode signals with the same or different phase delays; and a circuit element configured to simultaneously combine or distribute the OAM mode signals by controlling phases of output signals output through the four output ports to be different depending on the OAM mode signals received through the input ports.