To improve the stability of a mechanism for preventing the collapse of an earth retaining wall, and efficiently enhance collapse preventing effects on the earth retaining wall.

In a supporting method for an earth retaining wall 1, an arm member 20 is joined to the head of the earth retaining wall 1 so as to extend to the rear side of the earth retaining wall 1, a ground anchor 30 is placed in a ground on the rear side of the earth retaining wall 1, and a PC steel twisted wire 2 for the ground anchor 30 is fastened to the arm member 20, thereby imparting a moment M to the head of the earth retaining wall 1.