To form a desired concrete placing surface by maintaining the original form of a sheathing board even if a fastening torque of a member for fixing a separator is not completely managed constantly.

In a formwork which has a sheathing board with its front face being concrete placing surface and in which a crosspiece is installed on its rear face to reinforce the sheathing board and receive and support a fastening pipe to be used in a formwork timbering, a separator 17 is arranged between front faces of the opposing sheathing boards 11 and a fixing member 18 for fixing the separator is arranged outside each sheathing board, for which shank through holes 20 through which the separator and the fixing member are put are arranged in the peripheral parts of the sheathing boards. The shank through holes are formed as recessed cutout parts in the crosspieces 12 installed in the peripheral parts of the sheathing boards so that when a plurality of formworks 10 are arranged adjacent each other, the shank through holes are put together to compose one shank through hole.