PURPOSE: To suppress expansion and deformation, prevent the occurrence of cracks, and improve the yield strength of a tension steel by forming peripheral projections and ridge-shaped projections on a tube body for grout used for the underground installation of the tension steel and arranging reinforcing materials.

CONSTITUTION: When an anchor is to be installed, a tension steel P is stored in a tube body 1 for grout, it is inserted into a hole dug in the ground, mortar or the like is injected to the inside and outside of the tube body 1 before or after it. Many peripheral projections 2 are protruded spirally or in a collar shape in the circumferential direction on the outside of this tube body 1, one or multiple continuous linear ridge-shaped projections 3... are protruded in the lengthy direction. Multiple reinforcing materials 4... are linearly buried on wall bodies 31 of the ridge-shaped projections 3... over the whole length of the tube body 1. The firm resistance against the strong tensile force can be obtained.