An electrochemical reaction device includes: a first reactor including a first room and a second room, the first room being configured to store a gas containing carbon dioxide or a first electrolytic solution containing carbon dioxide, and the second room being configured to store a second electrolytic solution containing water; a cathode disposed in the first room, the cathode being configured to reduce the carbon dioxide and thus produce a reduction product; an anode disposed in the second room, the anode being configured to oxidize the water and thus produce an oxidation product; a first pressure adjuster configured to adjust pressure in the first room; a temperature detector configured to detect a temperature in the first reactor to form a detection signal; and a controller configured to control the pressure adjuster in accordance with the detection signal from the temperature detector.