PROBLEM TO BE SOLVED: To obtain a general-purpose dissolution aid which has high solubility in the production of an aqueous insect killing solution of a specified pyrethroid-based compound.SOLUTION: In the aqueous insect killing solution comprising: a pyrethroid-based compound (A) and a surfactant (B), aliphatic diesters and/or aromatic ethers are used as a dissolution aid (C). It is particularly preferable that the mass ratio of (C)/(A) is 0.5 to 15, and also, the mass ratio of (B)/(C) is 1 to 20 in the aqueous insect killing solution.