To simplify the operation of interconnecting a plurality of split blocks.

A connecting fitting 2 is fixed to a core form 23 by a shank 35. Thereafter concrete is placed into a form 10 whereby the bent surface plate 6 of the connecting fitting 2 is buried into the connecting end face 1A of an arched block 1 formed by the form 10. Also, the core form 23 forms an approximately hemispherical recess 7 in the inner wall 1B of the block 1 facing a surface plate portion 5. Thus when the blocks 1 are interconnected, the connecting end faces 1A of the blocks 1 are butted against one another and bolts passed through the through holes 4 of the connecting fittings 2 and nuts are tightened together whereby the blocks 1 can be interconnected.