A sterile carbonated beverage filling system, comprising: a beverage sterilizing section which sterilizes a raw material liquid to prepare a sterilized beverage; a beverage cooling section which cools the sterilized beverage prepared by the beverage sterilizing section; a carbonated beverage producing section which injects carbonic acid gas into the sterilized beverage cooled by the beverage cooling section to prepare a sterile carbonated beverage; a carbonated beverage filling section which fills the sterile carbonated beverage, prepared by the carbonated beverage producing section, into a bottle; and a beverage supply pipeline which connects the beverage sterilizing section, the beverage cooling section, the carbonated beverage producing section, and the carbonated beverage filling section, characterised in that the beverage supply pipeline comprises a pump (53, 56, 59) having a casing, a rotating shaft as a rotating body, a substantially cylindrical connecting portion as a non-rotating body and through which the rotating shaft is inserted, an impeller disposed in the casing, and a motor connected to the impeller via the rotating shaft and rotating the impeller to feed the sterilized beverage from a beverage inlet of the casing to a beverage outlet of the casing, the beverage inlet and the beverage outlet being connected to the beverage supply pipeline, and a mechanical seal portion, wherein the connecting portion is provided between the casing and the mechanical seal portion and the mechanical seal portion comprises an internal space and a sterile water inlet and a sterile water outlet, the sterile water inlet and the sterile water outlet being communicated with the internal space, wherein the sterilized beverage or the sterile carbonated beverage is flowed through the casing, wherein a boundary surface between the rotating shaft and the connecting portion of the pump (53, 56, 59) is sealed with sterile water in the mechanical seal portion at a temperature of 1°C or more and 40°C or less, so as to reduce a rising in a temperature of the sterilized beverage or the sterile carbonated beverage staying in the casing, and wherein the internal pressure of the mechanical seal portion sealing the boundary surface is lower than the internal pressures of the beverage supply pipeline and the casing. a beverage sterilizing section which sterilizes a raw material liquid to prepare a sterilized beverage; a beverage cooling section which cools the sterilized beverage prepared by the beverage sterilizing section; a carbonated beverage producing section which injects carbonic acid gas into the sterilized beverage cooled by the beverage cooling section to prepare a sterile carbonated beverage; a carbonated beverage filling section which fills the sterile carbonated beverage, prepared by the carbonated beverage producing section, into a bottle; and a beverage supply pipeline which connects the beverage sterilizing section, the beverage cooling section, the carbonated beverage producing section, and the carbonated beverage filling section, characterised in that the beverage supply pipeline comprises a pump (53, 56, 59) having a casing, a rotating shaft as a rotating body, a substantially cylindrical connecting portion as a non-rotating body and through which the rotating shaft is inserted, an impeller disposed in the casing, and a motor connected to the impeller via the rotating shaft and rotating the impeller to feed the sterilized beverage from a beverage inlet of the casing to a beverage outlet of the casing, the beverage inlet and the beverage outlet being connected to the beverage supply pipeline, and a mechanical seal portion, wherein the connecting portion is provided between the casing and the mechanical seal portion and the mechanical seal portion comprises an internal space and a sterile water inlet and a sterile water outlet, the sterile water inlet and the sterile water outlet being communicated with the internal space, wherein the sterilized beverage or the sterile carbonated beverage is flowed through the casing, wherein a boundary surface between the rotating shaft and the connecting portion of the pump (53, 56, 59) is sealed with sterile water in the mechanical seal portion at a temperature of 1°C or more and 40°C or less, so as to reduce a rising in a temperature of the sterilized beverage or the sterile carbonated beverage staying in the casing, and wherein the internal pressure of the mechanical seal portion sealing the boundary surface is lower than the internal pressures of the beverage supply pipeline and the casing.