A liquid container manufacturing method for manufacturing, from a closed-bottom tubular-shaped preform, a liquid container containing a content liquid by using a nozzle unit and a mold, the nozzle unit including: a blow nozzle that defines a liquid supply port positioned at a termination of a liquid supply path connected to a pressurized liquid supply source; a discharge rod including a discharge port connected to a liquid drawing source through a discharge path; and a gas supply port that is provided in the blow nozzle and that is connected to a pressurized gas supply source, the liquid container manufacturing method comprising: a liquid blow molding step of molding the preform into the liquid container having a shape conforming to an inner surface of the mold, by supplying a pressurized liquid into the preform through the liquid supply port by the pressurized liquid supply source; and a headspace formation step of forming a headspace in the liquid container, by discharging, in a state in which the liquid supply path is closed, the liquid out of the liquid container through the discharge port positioned below the liquid supply port, the discharge accomplished by drawing-in by the liquid drawing source, wherein in the headspace formation step, a pressurized gas is supplied from the pressurized gas supply source into the liquid container through the gas supply port to thereby assist the discharge, by the drawing-in, of the liquid out of the liquid container through the discharge port, and characterized in that, when a pressure in the discharge path has increased to a set value, the supply of the pressurized gas by the pressurized gas supply source is stopped. a blow nozzle that defines a liquid supply port positioned at a termination of a liquid supply path connected to a pressurized liquid supply source; a discharge rod including a discharge port connected to a liquid drawing source through a discharge path; and a gas supply port that is provided in the blow nozzle and that is connected to a pressurized gas supply source, the liquid container manufacturing method comprising: a liquid blow molding step of molding the preform into the liquid container having a shape conforming to an inner surface of the mold, by supplying a pressurized liquid into the preform through the liquid supply port by the pressurized liquid supply source; and a headspace formation step of forming a headspace in the liquid container, by discharging, in a state in which the liquid supply path is closed, the liquid out of the liquid container through the discharge port positioned below the liquid supply port, the discharge accomplished by drawing-in by the liquid drawing source, wherein in the headspace formation step, a pressurized gas is supplied from the pressurized gas supply source into the liquid container through the gas supply port to thereby assist the discharge, by the drawing-in, of the liquid out of the liquid container through the discharge port, and characterized in that, when a pressure in the discharge path has increased to a set value, the supply of the pressurized gas by the pressurized gas supply source is stopped. a liquid blow molding step of molding the preform into the liquid container having a shape conforming to an inner surface of the mold, by supplying a pressurized liquid into the preform through the liquid supply port by the pressurized liquid supply source; and a headspace formation step of forming a headspace in the liquid container, by discharging, in a state in which the liquid supply path is closed, the liquid out of the liquid container through the discharge port positioned below the liquid supply port, the discharge accomplished by drawing-in by the liquid drawing source, wherein in the headspace formation step, a pressurized gas is supplied from the pressurized gas supply source into the liquid container through the gas supply port to thereby assist the discharge, by the drawing-in, of the liquid out of the liquid container through the discharge port, and characterized in that, when a pressure in the discharge path has increased to a set value, the supply of the pressurized gas by the pressurized gas supply source is stopped.