Provided are a pest control composition containing a new active ingredient and being useful for preventing harmful organisms and a method of using same, and a new quinoline-based compound. Provided are a pest control composition containing, as active ingredients, a compound expressed by formula (1) or a salt thereof, and one or more kinds of ingredient selected from quinoline-based compounds and having pest control activity, and a new quinoline-based compound having pest control activity. In the formula, R1 represents a replaceable C1-C6 alkyl group, a C1-C6 haloalkyl group, etc., R2 represents a halogen atom, a replaceable C1-C6 alkyl group, a replaceable C1-C6 alkoxy group, etc., R3 represents a hydrogen atom, a halogen atom, a replaceable C1-C6 alkyl group, etc., n represents an integer in the range 0 to 5, X represents an oxygen atom or a sulfur atom, Y represents a phenyl group having a substituent at the ortho position, a pyridyl group, etc., and the bond including a broken line part represents a double
