To provide a fixing member for isolation system which can surely fix the isolation system to a free access floor in such a condition that the isolation system installed on the free access floor is not lifted or fallen with respect to a floor panel when an earthquake occurs.

A fixing hardware 36 includes a body 41, a pressing plate 38, and a U bolt 45. The body 41 is a plate member having a profile in an L character of cross section and has 2 surfaces of receiving member joining section 39 and supporting leg securing section 43. A notch section 42 through which a supporting leg 19 penetrates is provided in the supporting leg securing section 43. The pressing plate 38 is a plate member shaped in the L character of cross section, and installed so that one side surface may close an opening section of U character shaped notch section 42, and the other side surface of the pressing plate 38 is turned to a receiving member joining section 39 side of the body 41, and penetrated by the U bolt 45 from the receiving member joining section 39 side for fixing by a nut.