Liquefied gas treatment system

A liquefied gas treatment system (2) according to the present invention includes a boil-off gas heat exchanger (60) exchanging heat between boil-off gas, pressurized by a boil-off gas compressor (50) and recovered along a boil-off gas supply line branching off upstream of a liquefied gas-consuming unit (20), and the boil-off gas, supplied from a liquefied gas storage tank (10), wherein the boil-off gas heat exchanger (60) exchanges heat between the boil-off gas, pressurized by the boil-off gas compressor and recovered along the boil-off gas supply line, and flash gas (17), supplied through a vapor recovery line.