Glaciological surveys and glacier balance studies in the Mongolian Altai Mountains are necessary for understanding the impact of climate change within the area.　Such studies are important globally because the data can help expand the range of monitoring of the worldwide glacier observation network.　We estimated the glacier-wide surface mass balance (ΔM) of the Potanin Glacier in the Mongolian Altai Mountains by means of stake observations, pollen analyses, and pit observations.　We estimated ΔM as －0.97, －1.23, and －0.17 m w.e. (water equivalents) for the years 2005, 2008, and 2009, respectively.　The high negative value of mass balance observed in 2008 was due to lower amounts of solid precipitation and higher summer temperatures in comparison with 2005 and 2009.　A comparison of the Potanin Glacier with the Maliy Aktru Glacier in the Russian Altai Mountains, both locate in the slightly drier and warmer climate region, revealed that the two glaciers experienced similar mass balance fluctuations between 2005 and 2009, which was probably because these two glaciers are from the same regional climate system.　However, the ΔM of the Potanin Glacier in 2008 (－1.23) was more negative than that of the Maliy Aktru Glacier (－0.87).　Thus, we concluded that the lower value of ΔM at the Potanin Glacier compared with that of the Maliy Aktru Glacier was due to the smaller accumulation area ratio (AAR) as the higher equilibrium line altitude of the glacier.