The present invention relates to a method for purifying an immunoglobulin, and more particularly, to a method for purifying an immunoglobulin, which comprises: dialyzing and concentrating an immunoglobulin-containing plasma protein fraction II paste; removing thrombotic substances from the dialyzed and concentrated fraction by a purification process using ceramic cation exchange resin; and performing elution while maintaining salt concentration at a constant level to maintain the polymer content of the immunoglobulin at a low level. When the immunoglobulin purification method according to the present invention is used, the efficiency with which impurities and thrombotic substances are removed can be increased and the polymer content of the immunoglobulin can be maintained, and thus a stable immunoglobulin with improved quality can be produced.