We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet–star mass ratio of q=[9. 5±2. 1]× 10− 5 via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the Microlensing Observations in Astrophysics survey, real-time light-curve monitoring and intensive follow-up observations. A Bayesian analysis returns the stellar mass and distance at Ml= 0. 64+ 0. 21− 0. 26 M⊙ and Dl= 5. 9+ 0. 9− 1. 4 kpc, respectively, so the mass and separation of the planet are Mp= 20+ 7− 8 M⊕ and a= 3. 3+ 1. 4− 0. 8 AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprises four cold Neptune/super-Earths, five gas giant planets, and another sub-Saturn mass planet whose nature is unclear. The discovery of these 10 cold exoplanets by the microlensing method implies that the mass ratio function of cold exoplanets scales as dNpl/d log q∝ q− 0. 7±0. 2 with a 95% confidence level upper limit of n<− 0. 35 (where dNpl/d log q∝ qn). As microlensing is most sensitive to planets beyond the snow-line, this implies that Neptune-mass planets are at least three times more common than Jupiters in this region at the 95% confidence level.