A method for producing an internal olefin by stably isomerizing an α-olefin by using an inexpensive zeolite catalyst while preventing an oligomerization reactionis provided. The method for producing an internal olefincomprises a step of isomerizing an α-olefin having from16 to 18 carbon atoms by passing through a zeolite catalyst bed, wherein the α-olefin having from 16 to 18 carbon atoms is circulated through and brought into contactwith the zeolite catalyst bed before starting the isomerization reaction.