A vaporizer for generating a process gas from a liquid material includes a container defining a process space of the vaporizer, and an injector having a spray port configured to spray the liquid material in an atomized state downward in the container. A lower block is disposed below the spray port inside the container such that a run-up space for the atomized liquid material is defined between the spray port and the lower block, and an annular space continuous to the run-up space is defined between an inner surface of the container and the lower block. First and second heaters are respectively provided to the container and the lower block, and configured to heat the atomized liquid material flowing through the annular space to generate the process gas. A gas delivery passage is connected to the container to output the process gas from the annular space.