The invention discloses a liquid gasifying device and a gasifying method thereof and belongs to the field of energy chemical industry. The liquid gasifying device comprises a shell, multiple heat medium nozzles and a heat medium distribution pipe net. The shell is provided with an inner cavity. The inner cavity is used for containing a steel bottle and a heat medium enabling liquid contained in the steel bottle to be gasified. The shell is provided with a shell opening used for placing and taking out the steel bottle. The multiple heat medium nozzles are arranged on the shell and used for injecting the heat medium into the inner cavity of the shell. The heat medium distribution pipe net communicates with the multiple heat medium nozzles and are used for transferring the heat medium to the multiple heat medium nozzles and controlling the injection amount and the injection speed of the multiple heat medium nozzles. The liquid gasifying device and the gasifying method thereof have the beneficial effects of being capable of improving use efficiency of the heat medium and gasifying efficiency of liquid, being capable of reducing frost damage to a pipeline and equipment from liquid, and thus prolonging the service life of the equipment. The liquid gasifying device and the gasifying method thereof improve responsiveness and precision of liquid to temperature in the gasifying process.