The present invention provides a new insect pest control agent that can instantly stop the movement of an insect pest and kill the insect pest, but that does not have a risk of explosion or ignition and that does not destroy the ozone layer and that has a low global warming potential, and therefore that can be safely used. An insect pest control agent comprising 1-chloro-3,3,3-trifluoropropene as an active agent solves the above problem.
