A vinyl compound is polymerized under suspension polymerization conditions by polymerizing the vinyl compound in a suspension polymerization medium containing, as the suspending agent, from 0.02 to 0.2 parts by weight of a polyvinyl alcohol polymer (A) having a degree of hydrolysis ranging from 60 to 95 mol % and a terminal mercapto group, based on 100 parts by weight of the vinyl compound. In another aspect of the invention, the suspending agent is a combination of said polyvinyl alcohol polymer (A) and a polyvinyl ester (B) having a degree of hydrolysis less than 60 mol %. The weight ratio of the two polymeric suspending agents (A)/(B) ranges from 40/60 to 95/5.