In a process for producing a vinyl chloride polymer by suspension polymerization in a polymerization vessel having a coating film of a polymer scale preventive agent on the polymerization vessel inner wall and other inner surfaces, the polymerization is initiated by introducing an oil-soluble polymerization initiator having 10-hour half-life temperature of from 30.degree. C. to 55.degree. C., at a particular position of the interior of the liquid phase of polymerization materials charged. The position satisfys the following expression: H.ltoreq.0.7H.sub.0 wherein H represents a height from the bottom of the polymerization vessel to the position where the polymerization initiator is introduced, and H.sub.0 represents a height from the bottom of the polymerization vessel to the liquid surface of the liquid phase. This process can effectively prevent polymer scales from adhering to the polymerization vessel inner wall of course and also to the baffle on its side facing the polymerization vessel inner wall at the gas/liquid interface and the vicinity thereof even with repetition of polymerization of vinyl chloride. Good formed products with less fish eyes can be obtained.