polymer particles having a small particle diameter and a narrow particle diameter distribution are obtained by a continuous polymerization method which does not accompany an increase of cohering products attaching to an inner face of a reaction vessel and an air - bubble invasion and , in which stirring of a material solution for polymerization is easy . an emulsion polymerization reaction or a suspension polymerization reaction is carried out by supplying a material solution for polymerization continuously to a clearance between coaxial double cylinders , which have stretched toward a direction crossing a horizontal plane , from the end side of the cylinders , by rotating at least one of the double cylinders round the axis and thereby , causing taylor vortices . the polymer particles thus - formed are obtained by through from the other end side of the double cylinders to the outside .