A liquid blow molding method of molding a preform into a liquid-containing container includes: a first nozzle descending step of descending a blow nozzle to a first position at which the blow nozzle does not seal the mouth part; a gas-liquid replacement step of supplying a liquid into the preform from the blow nozzle at the first position and discharging air inside the preform to outside; a second nozzle descending step of descending the blow nozzle to a second position at which the blow nozzle seals the mouth part, after the gas-liquid replacement step; and a blow molding step of supplying the liquid into the preform from the blow nozzle at the second position to blow mold the preform into the predetermined shape.