PURPOSE: To carry out blending continuously over a long period stbily and economically, by jetting a liquefied petroleum gas (LPG) into a liquefied natural gas (LNG) by the use of feed nozzle of the double pipe type having a liquid atomizing means at the tip of it, blending them.

CONSTITUTION: A heating medium having a temperature higher than freezing point of LPG is introduced through the feed pipe 7 to the interior of the outer pipe of the feed nozzle 2 of the double pipe type, and LPG at normal temperatureWa temperature lower than it is sent to the inner pipe. The heating medium is taken out from the channel 6 through the discharge pipe 8 to the outside of the system. LPG is sent from the channel 6 through the spray nozzle 9 at the tip of the nozzle, and jetted in a spray state to LNG flowing in the conduit 1. While LPG is circulated through the inner pipe and jetted from the spray nozzle 9, it is heated indirectly by the heating medium flowing in the outer pipe, so that freezing in the pipe is prevented.