A liquid mixing apparatus of the present invention includes: a first tank a first introduction section that introduces a first liquid into the first tank a second introduction section that introduces a second liquid into the first tank a first opening portion provided above a highest liquid level of the first tank a second tank a third introduction section that introduces a third liquid into the second tank a second opening portion provided above a highest liquid level of the second tank a liquid transfer conduit that connects a bottom surface portion of the first tank and a bottom surface portion of the second tank an opening/closing valve provided in the liquid transfer conduit a gas transfer conduit having one end arranged above the highest liquid level in the first tank and another end arranged above the highest liquid level in the second tank a pump capable of forward/reverse operation that can transfer a gas in two directions inside the gas transfer conduit and an atmospheric release control section that controls opening and closing of the first opening portion and the second opening portion.
