To provide a cage nut capable of being fitted in a support member with a fitting hole from a front surface side.

A cage nut 1 is fitted in a fitting hole 52 of a first member 51 from the front. A nut member 2 is located at an initial position where four corners 21b do not project from a bottom plate section 31 of a cage member 3. In the cage member 3, a slip-off prevention piece 33b abuts on a hole edge to be held. When a second member 61 is overlapped on a front surface of the first member 51, a bolt hole 62 is made to correspond to a screw hole 21a and a bolt 71 is screwed to the screw hole 21a, the nut member 2 co-rotates and stops at an action position where a side surface abuts on a holding piece 32 and a press-fit piece 33. In the state, the four corners 21b of a head section 21 project to a rear surface side of a hole edge of the fitting hole 52 and prevent the cage nut 1 from slipping off to the front. When the bolt 71 is fastened up to prescribed torque, a second member 61 is fixed to the front surface of the first member 51.