Provided is a fuel pressure monitoring system of a vaporizer using a safety module which issues a fault signal by detecting a pressure using a fuel pressure sensor disposed in a pressure regulating chamber of the vaporizer within a predetermined time after an engine is stopped and determining that the pressure regulating mechanism fails when the detected pressure exceeds a threshold stored in a storage device to be increased to a predetermined pressure or higher, and the pressure regulating mechanism is determined to fail only when a water temperature of cooling water in the engine of the vaporizer reaches a predetermined temperature at which warming up of the engine can be determined to be completed.