To provide foundation reinforcing pile which can firmly fix a continuous footing and mat foundation of a detached house to the ground and can sufficiently maintain functions of the continuous footing and mat foundation even if the ground is deformed.

A foundation reinforcing pile 10 comprises a pile form 14 located below a continuous footing and a mat foundation and embedded into the ground, a reinforcing steel 15 arranged in an internal space of the form 14, and concrete 16 placed into the internal space of the form 14. In the foundation reinforcing pile 10, a plurality of through holes 19 are formed in the peripheral surface 18 of the pile form 14, the reinforcing steel 15 has a first reinforcement part 24 extending upward from a top opening of the form 14 and a second reinforcement part located in the internal space of the form 14, and the concrete 16 has a reinforced concrete part 37 integrated with the second reinforcement part in the internal space of the form 14 and anchor parts 38 connected to the reinforced concrete part 37 and projecting into the ground from the through holes 19 of the peripheral surface 18.