A strain wave gearing (1, 1A, 1B, 1C, 100A, 100B, 100C) comprising: a rigid gear (2, 2A, 2B, 2C, 122, 142, 162); a flexible gear (3, 3A, 3B, 3C, 123, 143, 163) that is disposed coaxially with the rigid gear (2, 2A, 2B, 2C, 122, 142, 162) and is rotatable relative to the rigid gear (2, 2A, 2B, 2C, 122, 142, 162) about a center axis line of the rigid gear (2, 2A, 2B, 2C, 122, 142, 162); and a wave generator (4, 4A, 4B, 4C, 124, 144, 164) that is disposed coaxially with the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) and is rotatable relative to the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) about the center axis line, wherein the wave generator (4, 4A, 4B, 4C, 124, 144, 164) comprises: a plurality of gear pressing members (8, 8A, 8B, 8C, 148) that flex the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) in a radial direction at positions at equal angular intervals in a circumferential direction to form a plurality of meshing portions (5a, 5b, 125a, 125b, 145a, 145b, 165a, 165b) where the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) meshes with the rigid gear (2, 2A, 2B, 2C, 122, 142, 162); characterized in that the strain wave gearing (1, 1A, 1B, 1C, 100A, 100B, 100C) further comprises: an excitation unit (9, 9A, 9B, 9C, 129, 149, 169) that generates ultrasonic vibration of 20 kHz to 80 kHz in the respective gear pressing members (8, 8A, 8B, 8C, 148) in the radial direction. a rigid gear (2, 2A, 2B, 2C, 122, 142, 162); a flexible gear (3, 3A, 3B, 3C, 123, 143, 163) that is disposed coaxially with the rigid gear (2, 2A, 2B, 2C, 122, 142, 162) and is rotatable relative to the rigid gear (2, 2A, 2B, 2C, 122, 142, 162) about a center axis line of the rigid gear (2, 2A, 2B, 2C, 122, 142, 162); and a wave generator (4, 4A, 4B, 4C, 124, 144, 164) that is disposed coaxially with the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) and is rotatable relative to the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) about the center axis line, wherein the wave generator (4, 4A, 4B, 4C, 124, 144, 164) comprises: a plurality of gear pressing members (8, 8A, 8B, 8C, 148) that flex the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) in a radial direction at positions at equal angular intervals in a circumferential direction to form a plurality of meshing portions (5a, 5b, 125a, 125b, 145a, 145b, 165a, 165b) where the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) meshes with the rigid gear (2, 2A, 2B, 2C, 122, 142, 162); characterized in that the strain wave gearing (1, 1A, 1B, 1C, 100A, 100B, 100C) further comprises: an excitation unit (9, 9A, 9B, 9C, 129, 149, 169) that generates ultrasonic vibration of 20 kHz to 80 kHz in the respective gear pressing members (8, 8A, 8B, 8C, 148) in the radial direction. a plurality of gear pressing members (8, 8A, 8B, 8C, 148) that flex the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) in a radial direction at positions at equal angular intervals in a circumferential direction to form a plurality of meshing portions (5a, 5b, 125a, 125b, 145a, 145b, 165a, 165b) where the flexible gear (3, 3A, 3B, 3C, 123, 143, 163) meshes with the rigid gear (2, 2A, 2B, 2C, 122, 142, 162); characterized in that the strain wave gearing (1, 1A, 1B, 1C, 100A, 100B, 100C) further comprises: an excitation unit (9, 9A, 9B, 9C, 129, 149, 169) that generates ultrasonic vibration of 20 kHz to 80 kHz in the respective gear pressing members (8, 8A, 8B, 8C, 148) in the radial direction.