An emulsion of a nitrogen atom-containing polymer or salt thereof and a method for producing it are provided. The emulsion has high stability and low dispersity of the particle diameter of emulsified particles. A method for producing particles including a crosslinked nitrogen atom-containing polymer or sat thereof using the emulsion is also provided. The method for producing the emulsion includes a step of mixing a first solution that includes a nitrogen atom-containing polymer or salt thereof and a hydrophilic solvent and has a viscosity of 10 to 2,000 mPa·s, and a second solution that includes a hydrophobic solvent and has a viscosity of 1 to 100 mPa·s, stirring the mixture, and thus obtaining an emulsion of the nitrogen atom-containing polymer or salt thereof, wherein a ratio between the viscosity of the first and second solutions is in a range of 0.1:1 to 300:1.