Process for producing a vinyl chloride-based polymer

There is provided a process for producing a vinyl chloride-based polymer by conducting a suspension polymerization in an aqueous medium using an oil soluble polymerization initiator, wherein the oil soluble polymerization initiator utilizes a combination of (A) t-amyl peroxyneodecanoate and (B) a peroxide-based polymerization initiator with a 10 hour half-life temperature in a solution with a concentration of 0.1 mol/liter in trichloroethylene within a range of at least 30° C. but less than 55° C., and when a predetermined polymerization conversion rate is reached, the polymerization reaction temperature is raised by a predetermined amount, followed by addition of an antioxidant to said polymerization mixture to halt the polymerization reaction. According to this process, a vinyl chloride-based polymer with good anti-initial discoloration can be produced in high yield and with good productivity.