A smoothing method includes: a step of attaching a workpiece to a rotating shaft of a rotating mechanism; and a step of performing direct pressure blasting on the workpiece while rotating the workpiece about the rotating shaft as an axial center. In the blasting, injection media are injected in a direction orthogonal to the rotating shaft, the injection media include a core material made of an elastic body and abrasive grains provided on a surface of the core material, and hardness of the core material is lower than hardness of the abrasive grains.