To provide an underground anchor with expansion blades in which the expansion blades can be expanded even under the compacted ground only by using a hammer or the like for driving.

A pile body 1 to be driven into the ground and expansion blades 4 axially mounted to a side face of the pile body 1 by a rotary shaft 5 are configured. The expansion blades 4 include a lower blade 4A overlapped from the rotary shaft 5 in a length direction below the pile body 1. The expansion blades 4 include an upper blade 4B spread from the rotary shaft 5 to an obliquely outer side above the pile body 1. The lower blade 4A and the upper blade 4B are spread toward the outside of the pile body 1 around the rotary shaft 5. A pair of expansion blades 4 are formed. The upper blades 4B of the expansion blades 4 are connected while turning to left and right sides of the pile body 1.