To provide a spreading anchor capable of eliminating generation of excessive fastening of a screw by giving a sense of fastening when screw driving is conducted, eliminating management at the working site for screw driving using a screw driver, and giving a proper strength of the anchor.

The spreading anchor is composed of a first group of arms 5 each furnished with a head 4 at one end of its trunk 3 having a through-hole 2 in the axial direction and capable of spreading outward for a specified length from the other end and a second group of some longer arms 6 concentrating inward from the ends of the arms 5 to be consolidated in the central part. A screw admitting means is provided in the converging part 7 of the second group of arms 6, and a rod 10 to be inserted into the through-hole 2 in the trunk 3 in a movable state in the axial direction is furnished with an inserting means for a screw in its axial direction and has a length approximately equal to the distance between the head 4 of the anchor 9 and the converging part 7 of the second group of arms 6 a spread state of the first group of arms 5 and the second group of arms 6.