Abstract: There is disclosed a process for continuously producing a highly syndiotactic styrenic polymer by using a horizontal self-cleaning type reactor which comprises feeding into the reactor, a catalyst or both the catalyst and a styrenic monomer dividedly into at least two portions, preferably 2 to 5 portions in the direction of the axis of the reactor. The above process facilitates the control for the reactor inside temperatures because of the stepwise feeding of the catalyst (and the styrenic monomer) and remarkably enhances the productivity by simply increasing the feed rates of the catalyst and the styrenic monomer, thus making itself industrially highly valuable.