Provided is a method for manufacturing a molten salt battery, the method comprising: a housing step (S100) for housing a positive electrode, a negative electrode and a separator in a battery container; an injecting step (S110) for injecting the molten salt into the battery container while heating the battery container; a closing step (S120) for closing the battery container with a closing lid; a heating and drying step (S130) for heating the battery container in a vacuum state with a check valve open; and a sealing step (S150) for closing the check valve. In summary, the positive electrode, negative electrode, separator and molten salt are heated and dried in a vacuum state.