The present invention provides a waveguide for transmitting electromagnetic wave signals, configured such that a boundary condition between a dielectric and a conductor and a boundary condition between dielectrics are both present as boundary conditions applicable to the signals transmitted via the waveguide, the waveguide comprising: a first dielectric part comprising a dielectric; a conductor part covering a part of the first dielectric part; and a second dielectric part surrounding the first dielectric part and the conductor part.