Main Shaft of Half shaft as a part of drive system of a vehicle, delivers driving force generated from engine to torque by high-speed rotation. and this main shaft is consist of solid shaft which ensures durability. In case of applying tube shaft with friction welding as a method of changing product structure in order to weight lightening, annealing heat treatment process is required for stress relief of welded part to meet the same durability with solid shaft. It comes to the conclusion that it satisfies the durability, hardness equalization and stabilization of metal organization if annealing temperature applies from 450 ℃ to 500 ℃ as a post heat treatment on thermal effect boundary of friction welding.