A neutral particle beam processing apparatus comprises a process gas inlet port (11) for introducing a process gas into a vacuum chamber (1), a plasma generating chamber (2) for generating positive ions and electrons from the introduced process gas, and a negative ion generating chamber (3) for attaching electrons generated in the plasma generating chamber to the residual gas to generate negative ions. The neutral particle beam processing apparatus further comprises an ion extracting portion (4) for extracting the positive ions or the negative ions and accelerating the positive ions or the negative ions in a predetermined direction, and a neutralizing chamber (5) for neutralizing an ion beam generated by the ion extracting portion (4) to generate a neutral particle beam. The neutral particle beam generated in the neutralizing chamber (5) is applied to a workpiece (X).