To correspond to a shape of a shot-peening worked portion and to prevent a situation where shot media scatter around the worked portion. To achieve this object, a shot peening apparatus for hitting shot media B against a welded part W and for applying a compressive stress to the welded part includes a kinetic-energy applying unit 26 that applies kinetic energy to the shot media B by an oscillator 26b, and a surrounding unit that surrounds both a worked portion U including the welded part W and surroundings of the oscillator 26b, and that confines the shot media B within the surrounded region while changing a state to correspond to a shape of the worked portion U.