Abstract: The present invention provides a surface wave excitation plasma generator in which surface wave excitation plasma is efficiently generated. A surface wave excitation plasma generator including an annular waveguide and a dielectric tube is provided. The annular waveguide 2 includes an inlet 2a for introducing a microwave M, an end plate 2b for reflecting the microwave M introduced and propagating within the waveguide, and a bottom plate 2c on which slot antennas 2d are formed at a predetermined interval. When the wavelength of the microwave M in the waveguide is ?g, the length from position b through positions c, d, e to position f on the bottom plate 2c, i.e. the circumferential length (?×D1) of the annular waveguide, is set as 2 ?g, and the positions b, c, d, e, f are spaced apart at an interval of ?g/2. Since the slot antennas 2d are arranged at two positions c and e, the interval between these two slot antennas 2d is equal to the wavelength ?g in the waveguide.