To provide an anchor nut securing device which facilitates the securing of an anchor nut on the ceiling.

A seat is screwed down onto the outer peripheral surface of a force bar insertion guide pin having a through insertion hole of a force bar, the upper and lower positions of the seat are adjusted and furthermore, the anchor nut is screwed down and tightened at the lower end of the guide pin. The anchor nut being tightened is inserted into a lower hole and the surface of the seat is placed on the open surface of the lower hole to set the insertion depth of the anchor nut. The force bar is pressed to push a wedge body loaded into the anchor nut so that a split cylinder part is expanded to get the anchor nut dogged into a lower hole of a floor. In a securing tool thus arranged, a hydraulic cylinder mechanism which is driven with a hydraulic pressure generator to make a piston rod move forward or backward pushing the force bar in contact with it is linked to the force bar insertion guide pin through an adaptor.