A wood-preserving composition which comprises, as an active ingredient, at least one member selected from the group consisting of a compound represented by formula (1) [wherein: R represents a hydrogen atom, a methyl group, etc.; X represents a hydrogen atom, a fluorine atom, etc.; Z1 and Z2 independently represent a halogen atom, a C1 to C3 haloalkyl group, etc.; and Q represents a group such as a phenyl group, a 4-fluorophenyl group, a 4-pyridyl group, a thiomorpholine-oxalamino group, etc.], fluxametamide, fluralaner, afoxolaner and sarolaner and which is to be used in a treatment for preserving wooden materials, and a wood-preserving treatment method using the composition.
