To provide a method of sterilizing a paper container for liquid which can be aseptically filled in which a blank is continuously sterilized in a short period of time and which is formed from the blank.

The paper container includes a paperboard as a base material layer. The blank is formed from a laminate in which at least a polyethylene layer (outer layer)/a base material layer/a gas barrier layer/a polyethylene layer (inner layer) are sequentially laminated. A rectangular cylindrical sleeve is formed from the blank, and the bottom of the sleeve is molded and the paper container for liquid is formed. In the sterilizing method of the paper container for liquid, the inner face of the paper container for liquid is sterilized with hydrogen peroxide, liquid food subjected to sterilization treatment is aseptically filled in the paper container for liquid, and the container is sealed. One face or both faces of the blank are subjected to pulsed light sterilization in which the faces are sterilized by pulsed light.