PURPOSE: To provide a concrete shuttering for a block possessing a loose core which can perform easily and reliably detachment operation for providing a through hole by penetrating through a block body to be molded in relation to a concrete shuttering molding concrete.

CONSTITUTION: A concrete shuttering 1 for a block is comprised by abutting a cover plate which is inserted extending over between side plates 2, 2 of a frame body and provided on its one end part against the outside of a side plate 2 and fitting a barlike core 3 to the frame body by a connecting part provided on the other end part and the connecting part is constituted of a bolt 5 to be ejected through an end surface of the core 3, a nut 6 which has a smaller diameter than the minimum size of a section of the core 3 and screws on to the bolt 5 and a washer 9 which has formed a recessed part 10. The washer 9 holds a space between the washer 9 and the side plate 2 at the outside of the frame body 2 and is provided movably freely, the bolt 5 of the core 3 is fitted in the recessed part 10 and the core 3 is connected with the frame body since the nut 6 is screwed down through the washer 9.