A novel synthesis method of a triarylpyrazine derivative, in particular, a manufacturing method by which a triarylpyrazine derivative, in specific, a 2,3,5-triarylpyrazine derivative in which an aryl group at a 5-position includes a substituent having an electron-withdrawing property can be synthesized with high yield as compared to a conventional method is provided. By using a synthesis method in which a mixture including a 1-aryl-2-(methylsulfinyl)ethanone derivative, meso-1,2-diarylethylenediamine, and a dehydrogenation agent is irradiated with a microwave to be reacted, the above object is achieved.