To obtain a repellent having high safety and excellent repelling effect on insect pests, especially sanitary pests such as mosquito and fly and offensive pests such as slug and pill bug.

The insect pest repelling component of the repellent is α-methyl-γ-butyrolactone or α-methylene-γ-butyrolactone existing in the leaf of plants belonging to the genus Spiraea such as Spiraea thunberigii, Spiraea cantoniensis, Spiraea japonica and Spiraea prunifolia and industrially produced as a solvent or a resin raw material. The α-methyl-γ-butyrolactone or α-methylene-γ-butyrolactone is diluted with water or an alcohol together with a sustained release agent and a buffering agent and sprayed to an area desired to inhibit the approach of the insect or applying to the exposed skin in the form of cream mixed with the compound to attain mosquito repelling effect. It can be used by supporting on various materials according to the use.