To provide a method for stably obtaining polymer fine particles in reverse phase suspension polymerization of an N-vinyl carboxylic acid amide aqueous solution without using an excessive amount of an emulsifier.

A production method of an N-vinyl carboxylic acid amide polymer comprises: dropping a monomer aqueous solution containing N-vinyl carboxylic acid amide expressed by general formula CH₂=CHNHCOR (where R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms) into a dispersion medium containing a hydrocarbon solvent and an emulsifier; and carrying out water-in-oil type suspension polymerization. In the method, a part of the emulsifier in a predetermined amount is added to the dispersion medium prior to starting dropping the monomer aqueous solution, and further, the remaining emulsifier is sequentially added concurrently with addition of the monomer aqueous solution.