The method for producing pentamethylene diisocyanate includes a reaction step, in which carbonyl chloride is allowed to react with pentamethylenediamine to produce a reaction mixture containing pentamethylene diisocyanate and a tar component containing a chlorine-containing component; a heating step, in which the reaction mixture is heated; and a purification step, in which the reaction mixture after the heating step is purified to separate the pentamethylene diisocyanate from the tar component, wherein in the heating step, the reaction mixture is heated without removing the tar component from the reaction mixture.