A liquid container manufacturing method of manufacturing a liquid container that contains a content liquid from a synthetic resin preform, the method including an inflation body insertion step of inserting an inflation body into the preform; an air discharge step of discharging air out of the preform by inflating an inflation body in the preform; a mouth blocking step of blocking a mouth of the preform; an inflation body contraction step of contracting the inflation body with the mouth blocked; and a liquid blow molding step of molding the preform into a liquid container by supplying a pressurized liquid into the preform through a blow nozzle.