A floating fastener includes a mounting base member affixed to a first panel member, a rotary fastening member supported on an elastic member in the mounting base member for locking a second panel member to the first panel member through a rotary motion, and a cap member affixed to the head of the rotary fastening member and axially slidably coupled to the mounting base member and rotatable to shift inside longitudinal ribs relative to vertical guide grooves at a locating flange around the periphery of the mounting base member and to move the rotary fastening member between a locking position and an unlocking position.