An aseptic filling system comprising: a heat sterilizer that sterilizes a content by heat; and a filling machine that fills a bottle with the content sterilized by heat by the heat sterilizer ; wherein: the heat sterilizer includes a heating unit that heats the content, and a cooling unit that cools the content heated by the heating unit ; a circulation line that circulates aseptic water is connected between the heating unit and the cooling unit , characterised in that the circulation line includes a heating-water line that supplies the heating unit with heating water from the cooling unit , and a cooling-water line that supplies the cooling unit with cooling water from the heating unit ; wherein the heating-water line and the cooling-water line constitute a sealed circulation line closed to the outside; the hot water which has cooled the content at the cooling unit is supplied into the heating unit through the heating-water line , and heats the content at the heating unit , and, the cooling water which has heated the content at the heating unit is supplied into the cooling unit through the cooling-water line , and cools the content at the cooling unit , and the cooling-water line is provided with a connection line that supplies aseptic water to the filling machine. a heat sterilizer that sterilizes a content by heat; and a filling machine that fills a bottle with the content sterilized by heat by the heat sterilizer ; wherein: the heat sterilizer includes a heating unit that heats the content, and a cooling unit that cools the content heated by the heating unit ; a circulation line that circulates aseptic water is connected between the heating unit and the cooling unit , characterised in that the circulation line includes a heating-water line that supplies the heating unit with heating water from the cooling unit , and a cooling-water line that supplies the cooling unit with cooling water from the heating unit ; wherein the heating-water line and the cooling-water line constitute a sealed circulation line closed to the outside; the hot water which has cooled the content at the cooling unit is supplied into the heating unit through the heating-water line , and heats the content at the heating unit , and, the cooling water which has heated the content at the heating unit is supplied into the cooling unit through the cooling-water line , and cools the content at the cooling unit , and the cooling-water line is provided with a connection line that supplies aseptic water to the filling machine. the heat sterilizer includes a heating unit that heats the content, and a cooling unit that cools the content heated by the heating unit ; a circulation line that circulates aseptic water is connected between the heating unit and the cooling unit , characterised in that the circulation line includes a heating-water line that supplies the heating unit with heating water from the cooling unit , and a cooling-water line that supplies the cooling unit with cooling water from the heating unit ; wherein the heating-water line and the cooling-water line constitute a sealed circulation line closed to the outside; the hot water which has cooled the content at the cooling unit is supplied into the heating unit through the heating-water line , and heats the content at the heating unit , and, the cooling water which has heated the content at the heating unit is supplied into the cooling unit through the cooling-water line , and cools the content at the cooling unit , and the cooling-water line is provided with a connection line that supplies aseptic water to the filling machine. <EOS>