To provide a method for producing pure dicyclopentadiene and 5- ethylidene-2-norbornene, capable of simultaneously producing the products from crude dicyclopentadiene and 1,3-butadiene.

This method for producing the pure dicyclopentadiene and the 5-ethylidene-2-norbornene comprises simultaneously producing the pure dicyclopentadiene and the 5-ethylidene-2-norbornene from the crude dicyclopentadiene and the 1,3-butadiene, wherein the method includes the following processes: the crude dicyclopentadiene is subjected to decomposition reaction to be converted into cyclopentadiene; the cyclopentadiene and 1,3-butadiene are subjected to Diels-Alder reaction to be converted into 5-vinyl-2-norbornene; the 5-vinyl-2-norbornene and the cyclopentadiene are each separated from the reaction mixture of the preceding process to be recovered; and the 5-vinyl-2- norbornene is subjected to isomerization reaction to be converted into the 5- ethylidene-2-norbornene.