Provided are a waveguide with which strain and defect caused by a manufacturing process or the like or caused in a semiconductor in an initial stage or during operation are suppressed so that improvement and stabilization of characteristics are expected, and a method of manufacturing the waveguide. A waveguide (107) includes a first conductor layer (103) and a second conductor layer (104) that are composed of a negative dielectric constant medium having a negative real part of dielectric constant with respect to an electromagnetic wave in a waveguide mode, and a core layer (108) that is in contact with and placed between the first conductor layer and the second conductor layer, and includes a semiconductor portion (101). The core layer including the semiconductor portion has a particular depressed and projected structure extending in an in-plane direction.