A first introduction part that introduces, into the first tank and the first tank, the first fluid, a second introduction part that introduces the first tank to the second liquid, the liquid mixing apparatus of the present invention, the maximum of the first tank a third introduction part that introduces the second vessel and the first opening provided above the water level, and a second tank, a third liquid, a second that is provided above the maximum water level of the second vessel a liquid transfer line that connects the opening, the bottom portions of the second tank and the first tank, an opening and closing valve provided in the liquid transfer line, one end distribution above the maximum water level in the first tank and gas transfer conduit is set, the other end of which is disposed above the highest water level in the second tank, and a forward and reverse operation can pump transfer in both directions, the first gas in the gas transfer line within I is provided with a, the atmosphere opening control section for controlling the opening and closing of the second opening and the first opening.本発明の液体混合装置は、第1槽と、第1液を第1槽に導入する第1導入部と、第2液を第1槽に導入する第2導入部と、第1槽の最高水位よりも上方に設けられた第1開口部と、第2槽と、第3液を第2槽に導入する第3導入部と、第2槽の最高水位よりも上方に設けられた第2開口部と、第1槽及び第2槽の底面部同士を接続する液体移送管路と、液体移送管路に設けられた開閉弁と、一端が第1槽内の最高水位よりも上方に配設され、他端が第2槽内の最高水位よりも上方に配設された気体移送管路と、気体移送管路内において気体を双方向に移送可能な正逆運転可能なポンプと、第1開口部及び第2開口部の開閉を制御する大気開放制御部と、を具備する。
