The first observation of the 3S-4S stimulated electronic Raman scattering (SEES) in sodium vapor with the infrared output tunable from 2.38μm to 2.65μm is reported. The calculation for the power gain factors and the measurment for the infrared output as a function of a dye laser tunning are made and both results are in good agreement. The pumping threshold in dependence of sodium vapor pressures are measured. The photon-conversion efficiency is about 30%. Simultaneously, the amplified spontaneous emission (ASE) on the Na 4S-3P transition is aleo observed.