To provide a foundation reinforcement technique for structure that can reinforce foundations of a structure against horizontal external force without letting equipment for work and a worker be in an adjacent site nor putting a fixation length part of an anchor in the adjacent site.

An anchor (4) is installed from an extra installation part (3) of a foundation (1) of the structure, and the installation angle of the anchor (4) is inclined in a horizontal direction (H) to a perpendicular direction (V) so that the anchor passes through an area under the ground right below foundations (1, 3) to be reinforced. A continuous fiber reinforcing material (41) is used as a tension support member for the anchor (4), and a tension member (10) composed of the continuous fiber reinforcing material or a wire member is wound around the foundations to be reinforced.