The invention relates to a filling device, in particular to a marine filling machine for a liquefied natural gas (LNG) filling ship or an LNG filling wharf boat, belonging to the technical field of ships. The filling machine comprises a liquid inlet system, a return-flow system, a control system and a pressure diffusing system, wherein the pressure diffusing system comprises a diffusing pipeline of the liquid inlet system and a diffusing pipeline of the return-flow system. The filling machine is simple in structure, high in safety factor, easy to operate and low in cost.