In order to provide a chemical reaction apparatus that can suppress a situation where microwaves are concentrated on a partial portion in a reactor, and that can more uniformly irradiate a content with the microwaves, a chemical reaction apparatus includes: a horizontal flow-type reactor in which a liquid content horizontally flows with an unfilled space being provided thereabove; a microwave generator that generates microwaves; and a waveguide that transmits the microwaves generated by the microwave generator to the unfilled space in the reactor, wherein a top of the reactor is curved with respect to a flow direction of the content.