To provide a temporary cutoff structure for resisting a shearing force by a simple constitution.

This temporary cutoff structure has a temporary cutoff work for surrounding the outer periphery of an underwater structure such as a bridge foundation, and is used in reforming by draining water from the inside of the temporary cutoff work. The temporary cutoff work has a plurality of annular assemblies 20 and an anchor 22. The assembly 20 is formed by mutually connecting a precast panel unit 26 of dividing an annular body having a prescribed height into a plurality in the peripheral direction by interposing a vertical sealant 28 between ends in the peripheral direction. A horizontal sealant 30 is interposed in upper-lower contact planes of the assemblies 20 laminated in the vertical direction, and a mutually fitting fitting part 32 is arranged. The fitting part 32 is formed into a recessed and projected fitting structure composed of a recessed part 33 and a projecting part 34. The fitting part 32 is arranged on upper-lower horizontal beams 26c and 26d. The recessed part 33 and the projecting part 34 exist in a central part in the width direction of the horizontal beams 26c and 26b, and are formed over the total length.