To obtain a polyorganosiloxane emulsion which has an excellent dispersion stability, a controlled mol.wt. distribution, and an excellent aging resistance in mol.wt. distribution by emulsifying a specific organosilicon compd. in a specified concn. in water at a specified temp., polycondensing the compd., and stopping the reaction when an aimed degree of polymn. is reached.

At least one organosilicon compd. of the formula: RaSi(OR1)4-a is emulsified and polycondensed in water in an amt. of 0.2 l per mol of the compd., pref. in the presence of an emulsifier comprising an anionic or cationic surfactant, at 15-100°C, and the polycondensation is stopped by neutralization when an aimed degree of polymn., e.g. 3-1,000, 000, is reached. The resultant emulsion pref. contains monodisperse particles having an average particle size of 10-500 nm, and thus an emulsifying machine such as a colloid mill or a pressure homogenizer can be dispensed with in the production process.