The optical device comprises a first substrate 10 having a control circuit
formed on; optical waveguide layer 40 formed above the first substrate
and having a refractive index changed by electro-optic effect; and second
substrates 14a, 14b having prism electrodes 18 for applying voltages to
the optical waveguide layer. The control circuit and the prism electrodes
are electrically connected to each other via columnar conductors 20. Even
in a case where thermal expansion coefficients of the control substrate
and of the light deflection substrates are very different from each
other, the pins are flexed corresponding to eternal forces, whereby
junction is protected from being damaged in the joining processing. Thus,
the optical switch can be highly reliable.