PURPOSE: To raise the durability of temporary cofferdam as well as make easier the installation and removal of the cofferdam by forming the body of the temporary cofferdam to be used for river, etc., into a beltlike shape by an integral press molding method.

CONSTITUTION: A flexible rubbery elastic beltlike body 1 reinforced with a canvas, etc., consists of a separating part 1a capable of forming a tubular shape when filled with a fluid, e.g., water, etc., and plate parts 1b provided on its both sides. When a temporary cofferdam is to be installed, struts 8 in two rows are provided at proper intervals in the bed 7 of a river, etc., and then a belt body 1' is provided between the struts 8. In this case, coupling metal tools 9 attached to the plate parts 1b on both sides are connected to the struts 8 in a slidable manner. Then, a fluid is filled through an inlet into the belt body 1' to make the separating part 1a of the belt body 1' a tubular, whereby forming a stable temporary cofferdam by the weight of water.