To provide a concrete form which is produced by reusing an existing form.

The concrete form is made up of placing panel sections 11 each having a concrete-placed rear surface and formed like a rectangular plane larger than a panel section 2 of the existing frame 1; outer frame sections 12 each erected along an outer peripheral edge of the placing panel section 11 and having first connection holes 13 formed therein at predetermined intervals; inner frame sections 14 each erected along a front face of the placing panel 11, and having a rectangular mounting section 17 for mounting the existing frame 1 therein; and reinforcing ribs 20 erected between the outer frame section 12 and the inner frame section 14.