Process for producing styrenic polymer

A process for producing a styrenic polymer having a wide molecular weight distribution, which comprises;

• adding to a styrenic monomer or a mixture of styrenic monomer and a monomer copolymerizable with the styrenic monomer, based on the total monomer, 50 to 5000 ppm by weight of at least one compound (A) selected from the group consisting of compounds having a dithiocarbamate group, sulfide compounds having at least one of an aryl group, an arylalkyl group and a thiazole group, based on the total monomer, and
• polymerizing the monomer in the presence of a radical initiator at a temperature of 90.degree. to 160.degree. C. to a final conversion of 40% by weight or more, said polymerization being carried out by a suspension polymerization, a batchwise bulk polymerization or a continuous bulk polymerization using a plug flow type polymerization reactor, wherein the styrenic polymer is produced having a molecular weight distribution of 2.5 or greater.