A sustained release pheromone preparation for controlling a pest insect comprising a solution of the sex pheromone thereof consisting of a mixture of an unsaturated aliphatic alcohol compound and its acetate compound, the unsaturated aliphatic acetate compound and the unsaturated aliphatic alcohol compound in a weight ratio of from 10:90 to 99.5:0.5, and a container for enclosing the mixture solution, the container comprising, as at least a part of the container, a membrane of a polyester corresponding to Formula or a polyester copolymer corresponding to formula: wherein R 1 and R 2 may be the same or different and each stands for a divalent hydrocarbon group having from 1 to 20 carbon atoms, m is an integer of 4 or more, n is 2 or 3, and x is the number of from 0.6 to 1.0, or a polymer blend of the polyester or the copolymer with a biodegradable polyester, in which blend the biodegradable polyester is present in an amount of up to 40 parts by weight relative to 100 parts by weight of the polyester or copolymer, wherein the preparation has a property that a ratio of a residual weight percentage of the remaining unsaturated aliphatic acetate compound to a residual weight percentage of a total of the remaining unsaturated aliphatic acetate and unsaturated aliphatic alcohol compounds, and a ratio of a residual weight percentage of the remaining unsaturated aliphatic alcohol compound to the residual weight percentage of the total of the remaining unsaturated aliphatic acetate and unsaturated aliphatic alcohol compounds fall each within a range of from 0.80 to 1.20, throughout an effective action period of the sustained release pheromone preparation, wherein the biodegradable polyester is selected from the group consisting of polycaprolactone, poly(3-hydroxybutyric acid), poly(3-hydroxyvaleric acid), poly(3-hydroxycaproic acid), and copolymers thereof, wherein the residual weight percentage means the percentage corresponding to the ratio of the remaining weight to the initial weight of the compound, and the effective action period means the period during which the residual weight percentage changes from 90% to 40%. a container for enclosing the mixture solution, the container comprising, as at least a part of the container, a membrane of a polyester corresponding to Formula or a polyester copolymer corresponding to formula: wherein R 1 and R 2 may be the same or different and each stands for a divalent hydrocarbon group having from 1 to 20 carbon atoms, m is an integer of 4 or more, n is 2 or 3, and x is the number of from 0.6 to 1.0, or a polymer blend of the polyester or the copolymer with a biodegradable polyester, in which blend the biodegradable polyester is present in an amount of up to 40 parts by weight relative to 100 parts by weight of the polyester or copolymer, wherein the preparation has a property that a ratio of a residual weight percentage of the remaining unsaturated aliphatic acetate compound to a residual weight percentage of a total of the remaining unsaturated aliphatic acetate and unsaturated aliphatic alcohol compounds, and a ratio of a residual weight percentage of the remaining unsaturated aliphatic alcohol compound to the residual weight percentage of the total of the remaining unsaturated aliphatic acetate and unsaturated aliphatic alcohol compounds fall each within a range of from 0.80 to 1.20, throughout an effective action period of the sustained release pheromone preparation, wherein the biodegradable polyester is selected from the group consisting of polycaprolactone, poly(3-hydroxybutyric acid), poly(3-hydroxyvaleric acid), poly(3-hydroxycaproic acid), and copolymers thereof, wherein the residual weight percentage means the percentage corresponding to the ratio of the remaining weight to the initial weight of the compound, and the effective action period means the period during which the residual weight percentage changes from 90% to 40%.