To provide a system for filling a paper container with liquid capable of reducing waste of energy by making use of waste heat from devices.

A system for filling a paper container with liquid which fills a paper container with liquid comprises: a liquid filling machine for filling a paper container with liquid; and a cooling machine for cooling a paper liquid container filled with liquid. The liquid filling machine includes bottom sealing means for sealing a bottom portion, filling means for filling the paper container with liquid, and top-sealing means for sealing a top portion after the liquid is fed. The bottom sealing means includes first heating means as a device for heating the bottom portion. The filling means includes second heating means as a device for warming liquid to be fed. The top sealing means includes third heating means as a device for heating the top portion.