Foundation mold

[Problem] To provide a mold that is light and exhibits little change in dimensions due to the ambient temperature. [Solution] A foundation mold 10 comprises a rectangular frame-shaped metal frame 20, and a resin surface plate 40 that is attached to the metal frame 20 and closes off an opening in the metal frame 20. The metal frame 20 comprises: a top plate 21 that include fitting notches 33; and L-shaped crosspieces 34. The resin surface plate 40 comprises protruding bodies 42 that fit with the fitting notches 33, and L-shaped slits 53 into which the crosspieces 34 are inserted. The resin surface plate 40 is attached to the metal frame 20 due to the protruding bodies 42 fitting with the fitting notches 33 and the crosspieces 34 being inserted into the slits 53. The attached resin surface plate 40 closes off an opening 38 in the metal frame 20. The fitting notches 33 and crosspieces 34 inhibit expansion and contraction of the resin surface plate 40 in a left-right direction 12.