The invention discloses a method and a device for producing diisobutylene, and belongs to the technical field of petrochemical industry. The device for producing diisobutylene, provided in the embodiment of the invention, inputs a first reaction material through a first feed port during production of the diisobutylene, outputs a reaction product separated from the first reaction material through afourth discharge port, inputs a an azeotrope of the reaction product and an inhibitor through a sixth feed port, outputs the reaction product separated from the inhibitor in the first reaction material through an eighth discharge port, and outputs the inhibitor separated from the reaction product in the azeotrope through a seventh discharge port. The device inputs the azeotrope of diisobutylene and tert-butyl alcohol into an extraction tower through the sixth feed port, the azeotrope is separated in the extraction tower, and the diisobutylene separated from the tert-butyl alcohol in the azeotrope is output as the product through the eighth discharge port in order to realize the separation of diisobutylene and tert-butyl alcohol in the azeotrope, so the purity and the yield of the diisobutylene are increased.