PROBLEM TO BE SOLVED: To provide a technique especially suitable for the extermination of bedbugs which are sucking pest insects and biting pest insects against humans and animals.SOLUTION: The method for controlling the bedbugs includes jetting the liquefied carbon dioxide gas containing α-cyano-3-phenoxybenzyl chrysanthemate dissolved therein, from a pressure-resistant container which is pressure-filled with the liquefied carbon dioxide gas so that the concentration of the α-cyano-3-phenoxybenzyl chrysanthemate may be within the range of 0.1-2.5 g/min a room.