A vaporization method includes a preparing step of preparing a vaporizing tube that covers at least a part of a heat exchange unit for cold energy of a Stirling engine and is capable of forming an ascending flow of the liquid flowing from a bottom to a top of the heat exchange unit for cold energy, and a vaporizing step of feeding the liquid in the vaporizing tube to thereby form the ascending flow and bringing the liquid into contact with the Stirling engine to vaporize the liquid. In the preparing step, a flowing direction of the ascending flow is adjusted to suppress occurrence of separated flows of the liquid and gas in the vaporizing tube. In the vaporizing step, the liquid is fed at a flow velocity at which a gas-liquid two-phase flow in which the liquid and the gas are mixed is formed in the vaporizing tube.