A lithium or lithium alloy film forming method comprises: the step of heating and evaporating lithium or lithium alloy under an atmosphere of inert gas in an ultra fine particle producing chamber to produce ultra fine particles of lithium or lithium alloy therein; the step of transporting the ultra fine particles through a transfer pipe with the inert gas into a film forming chamber under vacuum atmosphere; the step of jetting the ultra fine particles onto a substrate arranged in the film forming chamber from a nozzle; the step of moving a substrate holder holding the substrate in the X-direction and/or Y-direction; the step of preheating the substrate at a predetermined temperature within the range of 100 to the melting point of lithium or lithium alloy: and the step of forming a film of lithium or lithium alloy on the substrate being moved with the substrate holder.