PURPOSE: To obtain a concrete block molding frame capable of molding blocks having different curvatures in their surfaces with the same mold frame.

CONSTITUTION: The mold frame Includes a flexible face board 1 for molding the curved surface of a block, and the flexible face board 1 is connected to the support frame 3 in both end grain sides 13, 13 and intermediate part, and further at least one of the connecting parts in the end grain sides and connecting parts in the intermediate part has a jack 9 for allowing the flexible face board l to be shifted in the direction at face right angles with respect to the support frame 3. In order to make the flexible curved line of the flexible face board 1 arcuate, belt-like reinforcing ribs 15 intersecting with the end grain sides 13 are provided on the rear surface of the flexible face board, and notches 14 are made on the reinforcing ribs at distance to offset a distribution of bending stresses affecting the flexible face board 1. By operating the jack 9 and allowing the flexible face board 1 to curve, the curvature of the flexible face board 1 is varied, thus molding the curved surface of the block.