A multistage optical packet switching apparatus with self electro-optic-effect device is disclosed. The apparatus is formed with multistage structure using a plurality of symmetrical self electro-optic-effect devices, self-routing being performed by the control for a header part of optical packets after self-duplication and amplification for the input optical signal. The optical packet switching apparatus using a plurality of symmetrical self electro-optic-effect devices includes a front stage having first and second self electro-optic-effect devices interconnected and a back stage having third and fourth self electro-optic-effect devices interconnected, the 1.quadrature. multistage structure comprising the unit switching modules interconnected each comprising the front and the back stages, the self-duplication and amplification being performed in the front stage and the switching being performed in the back stage. The use of the apparatus is an optical exchange.