The present invention relates to an agitator for suspension polymerization having a more improved structure in effect in contrast to the earlier agitator. The present invention also relates to an improved suspension polymerization method of vinyl chloride using a polymerization reactor equipped with that agitator, by which vinyl chloride resin having excellent quality can be prepared with a diminution of the number of fish eyes which cause many problems such as deterioration of the processed article, low productivity, etc.