A one-way clutch for a wind power generation device, comprising: an inner ring provided on one rotating body out of an input rotating body provided so as to be integrally rotatable with the output shaft of a speed-up gear of a wind power generation device and an output rotating body provided so as to be integrally rotatable with a drive shaft of a power generator to which the rotation of the output shaft is transmitted and coaxially disposed radially inside or outside the input rotating body; an outer ring provided on the other rotating body and disposed radially outside the inner ring; and a plurality of engaging elements individually disposed in a plurality of spaces formed between both raceway faces (71a, 72a) of the inner ring and the outer ring, wherein, in a state in which a rotation speed of the input rotating body is higher than a rotation speed of the output rotating body, the engaging elements engage with both the raceway faces (71a, 72a) of the inner ring and the outer ring to connect the input rotating body to the output rotating body so that the rotors are integrally rotatable, and in a state in which the rotation speed of the input rotating body is lower than the rotation speed of the output rotating body, the engaging elements release the engagement to cut off connection between the input rotating body and the output rotating body, and characterized in that the plurality of engaging elements or the inner ring and the outer ring are made of a base material obtained by subjecting a martensitic stainless steel material to soft nitriding treatment such that Vickers hardness of a portion having a depth up to 20 μm from a surface of a contact portion where the base material contacts a mating member due to the sliding or engagement between the base material and the mating member is 1000 to 1500 Hv. an inner ring provided on one rotating body out of an input rotating body provided so as to be integrally rotatable with the output shaft of a speed-up gear of a wind power generation device and an output rotating body provided so as to be integrally rotatable with a drive shaft of a power generator to which the rotation of the output shaft is transmitted and coaxially disposed radially inside or outside the input rotating body; an outer ring provided on the other rotating body and disposed radially outside the inner ring; and a plurality of engaging elements individually disposed in a plurality of spaces formed between both raceway faces (71a, 72a) of the inner ring and the outer ring, wherein, in a state in which a rotation speed of the input rotating body is higher than a rotation speed of the output rotating body, the engaging elements engage with both the raceway faces (71a, 72a) of the inner ring and the outer ring to connect the input rotating body to the output rotating body so that the rotors are integrally rotatable, and in a state in which the rotation speed of the input rotating body is lower than the rotation speed of the output rotating body, the engaging elements release the engagement to cut off connection between the input rotating body and the output rotating body, and characterized in that the plurality of engaging elements or the inner ring and the outer ring are made of a base material obtained by subjecting a martensitic stainless steel material to soft nitriding treatment such that Vickers hardness of a portion having a depth up to 20 μm from a surface of a contact portion where the base material contacts a mating member due to the sliding or engagement between the base material and the mating member is 1000 to 1500 Hv.