A fatigue testing device for testing fatigue life of a test piece by having the test piece vibrate, the fatigue testing device comprising: a first fixing jig having a first fixing surface adapted for fixing thereto the test piece in a cantilever state; a vibrator (7, 8, 9, 10) adapted to cause the test piece to vibrate by action of blowing compressed gas in a pulse form onto the test piece; a displacement detector for detecting a vibration displacement of the test piece; a second fixing jig adapted for fixing the test piece interposed between the first fixing jig and the second fixing jig, wherein the second fixing jig has a second fixing surface adapted for fixing thereto the test piece in a cantilever state, between the first fixing surface and the second fixing surface, characterized in that each of both fixing surfaces (2a, 3a) has a curved shape such that, when a first end of a test piece being a metal plate is fixed between the first fixing surface and the second fixing surface, and a second end of said test piece is positioned between the first fixing surface and the second fixing surface, a first space is present between the test piece and the first fixing surface at a first location that is other than a location where the test piece is fixed, a second space is also present between the test piece and the second fixing surface at a second location that is other than the location where the test piece is fixed, and such that the first and second spaces increase with increasing distance from the location where the test piece is fixed, said second end of said test piece is able to vibrate between the first fixing surface and the second fixing surface when the compressed gas in pulse form is blown onto it, and wherein a first through hole that opens at the first fixing surface is provided in the first fixing jig, and wherein the displacement detector detects the vibration displacement of the test piece through the first through hole, and wherein a second through hole that opens at the second fixing surface is provided in the second fixing jig, and wherein the vibrator (7, 8, 9, 10) is adapted to cause compressed gas to be blown onto the test piece through the second through hole. a first fixing jig having a first fixing surface adapted for fixing thereto the test piece in a cantilever state; a vibrator (7, 8, 9, 10) adapted to cause the test piece to vibrate by action of blowing compressed gas in a pulse form onto the test piece; a displacement detector for detecting a vibration displacement of the test piece; a second fixing jig adapted for fixing the test piece interposed between the first fixing jig and the second fixing jig, wherein the second fixing jig has a second fixing surface adapted for fixing thereto the test piece in a cantilever state, between the first fixing surface and the second fixing surface, characterized in that each of both fixing surfaces (2a, 3a) has a curved shape such that, when a first end of a test piece being a metal plate is fixed between the first fixing surface and the second fixing surface, and a second end of said test piece is positioned between the first fixing surface and the second fixing surface, a first space is present between the test piece and the first fixing surface at a first location that is other than a location where the test piece is fixed, a second space is also present between the test piece and the second fixing surface at a second location that is other than the location where the test piece is fixed, and such that the first and second spaces increase with increasing distance from the location where the test piece is fixed, said second end of said test piece is able to vibrate between the first fixing surface and the second fixing surface when the compressed gas in pulse form is blown onto it, and wherein a first through hole that opens at the first fixing surface is provided in the first fixing jig, and wherein the displacement detector detects the vibration displacement of the test piece through the first through hole, and wherein a second through hole that opens at the second fixing surface is provided in the second fixing jig, and wherein the vibrator (7, 8, 9, 10) is adapted to cause compressed gas to be blown onto the test piece through the second through hole.