LIQUID HYDROGEN SYSTEM

A liquid hydrogen system (10) includes a hydrogen tank (12) mounted on a vehicle and configured to store liquid hydrogen, a supply circuit (30) configured to supply a hydrogen engine (100) with a hydrogen gas which is converted from the liquid hydrogen extracted from the hydrogen tank (12), and a return circuit (60) branched from the supply circuit (30) and connected to the hydrogen tank (12), the return circuit (60) being configured to return the hydrogen gas into the hydrogen tank (12) in such a manner that the internal pressure of the hydrogen tank (12) matches or exceeds a predetermined reference pressure (Pst).