Provided is a chemical reaction apparatus capable of efficiently irradiating a content with microwaves even in a case where the amount of the content changes, including: a horizontal flow-type reactor 13 inside of which has been partitioned into multiple chambers by a partition plate, and a liquid content horizontally flows with an unfilled space being provided thereabove; a microwave generator 14 that generates microwaves; and at least one waveguide 15 that transmits the microwaves generated by the microwave generator 14 to the unfilled space in the reactor 13; wherein the reactor 13 has a shape in which an area of a liquid surface does not change even in a case where a height of the liquid surface changes according to a change in an amount of the content.
