The present invention relates to a spacer member reducing fretting wear and fastened structures using a spacer member, furthermore, the present invention provides a spacer member 1 sandwiched between contact surfaces 7 of contact materials 6 subject to abrasion and suffering from wear and provided with sliding and vibrating surfaces 2, 2 characterized in that the sliding or vibrating surfaces (2, 2) of the spacer member 1 have a higher hardness than at least one of the contact surfaces (7) of the first contact material (6) and the second contact material (6′) and the sliding or vibrating surfaces (2, 2) of the spacer member 1 have a lower coefficient of friction and a higher flatness than at least one of the contact surfaces (7) of the first contact material (6) and the second contact material (6′), whereby the sliding or vibrating surfaces 2, 2 of the spacer member 1 do not easily wear down the contact surfaces 7 of the contact materials 6.