Abstract: A fastening structure inserts a threaded rod 11a of a bolt 11 through a fixing hole 12a of a to-be-fixed member 12 in a manner such that an end portion of the threaded rod protrudes from the fixing hole, and screwing a machine screw 15 with a proper torque into a nut 14 which is provided on the end portion via a washer 13. The washer has an inclined surface 13c formed on a first side 13b which faces the nut, and has a flat surface formed on a second side 13d. The machine screw is screwed into the nut in a direction such that an axis is orthogonal to the inclined surface 13c. The first side (the inclined surface) and the second side of the washer have a different surface roughness, and the first side has a smaller coefficient of friction than the second side.

Abstract: Provided is a lock washer (1) that is provided between a nut (4) and an attachment object (2), and made of first and second members (11), (12) used in a stacked state. The first member (11) includes an upper surface (11a) in which irregularities are formed radially so that resistance is smaller when a nut (4) is turned in a tightening direction, and frictional resistance is larger when the nut (4) is turned to a loosening side, and a lower surface (11b) in which slopes (11ba) are formed so as to be gradually lowered in height toward the tightening direction of the nut (4) along a circumferential direction.

Abstract: A fastening structure inserts a threaded rod 11a of a bolt 11 through a fixing hole 12a of a to-be-fixed member 12 in a manner such that an end portion of the threaded rod protrudes from the fixing hole, and screwing a machine screw 15 with a proper torque into a nut 14 which is provided on the end portion via a washer 13. The washer has an inclined surface 13c formed on a first side 13b which faces the nut, and has a flat surface formed on a second side 13d. The machine screw is screwed into the nut in a direction such that an axis is orthogonal to the inclined surface 13c. The first side (the inclined surface) and the second side of the washer have a different surface roughness, and the first side has a smaller coefficient of friction than the second side.