A dielectric line switch is provided which is capable of easily controlling the propagation of an electromagnetic wave. Also provided is an antenna device employing said dielectric line switch. As an embodiment of the invention, a plurality of dielectric lines and a plurality of primary radiators are provided on a rotary unit. With the rotation of the rotary unit, the dielectric lines are switched ON and OFF by virtue of mechanical means, so that a desired change-over may be effected among the plurality of primary radiators in a time sharing manner, and the positions of the primary radiators may be shifted within a plane of the focal point of a dielectric lens, thereby enabling the transmission wave beam and/or reception wave beam to scan in a desired manner.