A dielectric waveguide input/output structure is provided, which comprises an input/output point provided near the center on one side of a bottom surface of a rectangular parallelepiped-shaped dielectric body, wherein an outer periphery of the dielectric body is covered with an electrically conductive film, except for an L-shaped lateral part extending along an edge of the bottom surface from opposite sides of the input/output point and for a surrounding part of the input/output point in a lateral surface with which the input/output point is in contact.
