The invention relates to a microwave power confocal synthesis device. Aiming at the shortages that the microwave power synthesizer in the prior art has relatively high requirements on microwave sources, the system structure is complicated and the cost is high, the invention discloses a microwave power confocal synthesis device. The microwave power confocal synthesis device synthesizes the power of multiple paths of microwaves to obtain a large-power microwave, so that the cost of large-power microwave equipment is reduced. The technical scheme of the invention is that: the microwave power confocal synthesis device comprises at least two microwave input ends and the corresponding waveguide cavities. The waveguide cavity comprises a bottom surface, a top surface and a side wall vertical to the bottom surface and the top surface, wherein the bottom surface and the top surface are parallel to each other; the orthographic projection of the side wall on the bottom surface or the top surfaceis an elliptical arc; the microwave input end is arranged on a focus of the elliptical arc; the other focus of the elliptical arc is superposed and is a microwave gathering end; and the microwaves inputted by the microwave input ends are gathered at the microwave gathering end after passing through the waveguide cavities. The microwave power confocal synthesis device can be used for generating plasmas.