To provide a microwave plasma processing method wherein leakage prevention structure is installed on the whole periphery of an outer peripheral part of a plasma head, in order to prevent microwave from leaking from a gap between the plasma head and a substrate to be treated to the outside of the equipment, and to provide microwave plasma processing equipment and its plasma head.

When the microwave leakage prevention is performed by installing one or a plurality of the microwave leakage prevention structure bodies in the vicinity of the outer peripheral edge of the plasma head of the microwave plasma processing equipment, the microwave leakage prevention structure body is constituted of trench parts 60a, 60b, and the depth d of the trench parts is set as d=(2n-1)1/4λ where λis a free space wavelength of the microwave used in the microwave plasma processing and n is an integer.