The invention provides a connector-attached dielectric waveguide that allows the dielectric waveguide to be easily connectable with an opposite component and is capable of forming a connection structure exhibiting low transmission and return losses of a high frequency signal. The connector-attached dielectric waveguide includes a dielectric waveguide and a connector. The dielectric waveguide includes a dielectric waveguide body and a dielectric waveguide end. The dielectric waveguide end has a smaller cross-sectional area than the dielectric waveguide body.