To provide a foundation for a protective fence, by which the protective fence can be installed in a safe state without requiring much labor for installation.

A ring-shaped connecting part 2 is arranged at an end of a body 1. The connecting part 2 is placed over the ring-shaped connecting part 2 of another foundation for the protective fence. By inserting a supporting post 4 of the protective fence 3 into the stacked connecting parts 2, a plurality of the foundations can be connected to each other. The connecting part 2 can be arranged at the position where a protective surface 8 of the protective fence 3 projects forward from a front face of the body 1. The connecting part 2 may be cylindrical or formed with wire.