Provided are a sustained releaser of sex pheromone substances and a method for controlling insect pest by using the releaser, each enabling to control the simultaneous release of a mixture of sex pheromone substances having different chemical structures of one insect pest or a mixture of sex pheromone substances of insect pests, and each enabling to release the sex pheromone substances at a fixed rate or greater during the infestation period or periods of the respective insect pest or pests. More specifically, provided is a sustained releaser of sex pheromone substances comprising one or more first sex pheromone substances selected from linear aliphatic aldehyde having 10 to 18 carbon atoms, one or more second sex pheromone substances selected from aldehyde-free aliphatic derivatives having 7 to 20 carbon atoms, and first and second chambers each made of polymer material, wherein all of the first sex pheromone substances or all of the first sex pheromone substances and some of the second sex pheromone substances are enclosed in the first chamber and the remainder of the sex pheromone substances is enclosed in the second chamber.