To obtain a composition having an activity for a long period of time against a wood destroying insect.

This composition against a wood destroying insect contains (a) a compound having an insecticidal activity, (b) an organic natural compound or an organic synthetic material, or their mixture as a carrier material, (c) a compound having an activity to kill microorganisms as the case may be, (d) an attracting or a growth suppressing agent against the insect as the case may be and (e) an additive for blending as the case may be.