Automatic oil valve adjusting equipment for Shinkansen SMA spring opens/closes the two way valve unit of Automatic oil valve adjusting equipment for gear box according to oil temperature, the volume of oil flow lubricating the pinion gears is optimized. This system prevents the oil temperature from rising at the high speed travelling, and gives the Shinkansen stable run. It is used in the newest Shinkansen Nozomi-500 and 700 series.