The purpose of the present invention is to provide an electromagnetic wave emission device in which the destination to which an electromagnetic wave is supplied can be switched among a plurality of emission antennas, wherein there are no problems such as breakage of a switching element even in a case where a large-power electromagnetic wave is emitted. The present invention is an electromagnetic wave emission device characterized by the following: an electromagnetic wave output from an electromagnetic wave generator is distributed to a plurality of emission antennas, and then from among the plurality of emission antennas, a target antenna having plasma nearby is supplied with an electromagnetic wave distributed to the target antenna and all or part of the electromagnetic waves reflected by the emission antennas other than the target antenna; and the all or part of the electromagnetic waves distributed to the target antenna and all or part of the electromagnetic waves supplied to the target antenna after reflection by the emission antennas other than the target antenna are emitted from the target antenna to the plasma.