Abstract: The present invention relates to a reaction heat control mechanism of heat exchange area regulation type in a chemical reaction apparatus comprising: a reaction vessel for receiving a liquid agent to be reacted therein; a heater; a cooling jacket acting as an airtight vessel in and out of which a cooling medium flows; a temperature controller; and a cooling medium liquid- level controller acting as a supply and exhasut change mechanism for changing and regulating a volume of gas in the cooling jacket, said liquid level controller controlling the reaction heat of the liquid agent in the reaction vessel by increasing or decreasing a contact area of the cooling medium in the cooling jacket with the outer surface of the reaction vessel, and it can even control chemical reaction experiencing sudden temperature change in the reaction vessel in a quick and stable manner.