An aseptic filling method comprising: a preform sterilization step where a preform is sterilized; a preform heating step where the sterilized preform is heated to a molding temperature; a molding step where the heated preform is molded into a container by a molding unit ; a container sterilization step where the molded container is sterilized; a filling step where the sterilized container is filled with sterilized contents in an aseptic atmosphere; and a sealing step where the container filled with the contents is sealed by a sterilized lid member, the preform and the container being made to continuously travel, wherein assuming sterilizing ability in the preform sterilization step as X [LRV], the preform sterilization step being performed by performing any one, two or more selected from contact of a sterilizer with the preform , irradiation with electron beam to the preform , irradiation with light containing ultraviolet rays to the preform , contact of hot water with the preform , and contact of superheated steam with the preform and characterised in that assuming the sterilizing ability within a range from the preform heating step to the container sterilization step as Y [LRV], the container sterilization step being performed by performing any one, two or more selected from contact of a sterilizer with the container , irradiation with electron beam to the container , irradiation with light containing ultraviolet rays to the container , and contact of hot water with the container , a following formula is satisfied 5 ≤ X + Y ≤ 10 where Y ≥ 0 ; and wherein the molding unit is not sterilized, such that there is a possibility that the preform is contaminated with bacteria and the like during a period where the preform is conveyed through the molding unit . a preform sterilization step where a preform is sterilized; a preform heating step where the sterilized preform is heated to a molding temperature; a molding step where the heated preform is molded into a container by a molding unit ; a container sterilization step where the molded container is sterilized; a filling step where the sterilized container is filled with sterilized contents in an aseptic atmosphere; and a sealing step where the container filled with the contents is sealed by a sterilized lid member, the preform and the container being made to continuously travel, wherein assuming sterilizing ability in the preform sterilization step as X [LRV], the preform sterilization step being performed by performing any one, two or more selected from contact of a sterilizer with the preform , irradiation with electron beam to the preform , irradiation with light containing ultraviolet rays to the preform , contact of hot water with the preform , and contact of superheated steam with the preform and characterised in that assuming the sterilizing ability within a range from the preform heating step to the container sterilization step as Y [LRV], the container sterilization step being performed by performing any one, two or more selected from contact of a sterilizer with the container , irradiation with electron beam to the container , irradiation with light containing ultraviolet rays to the container , and contact of hot water with the container , a following formula is satisfied 5 ≤ X + Y ≤ 10 where Y ≥ 0 ; and wherein the molding unit is not sterilized, such that there is a possibility that the preform is contaminated with bacteria and the like during a period where the preform is conveyed through the molding unit . <EOS>