To provide a securing device of a mold of a concrete structure which can firmly secure the mold without creating any looseness of the mold into which concrete is poured.

The securing device of the mold of the concrete structure has a pair of angle bands 13, 14 and a pair of tie rods 15, 16. The pair of angle bands 13, 14 is formed so that each of them can be positioned along the shape of the curved sections which are opposite to each other in the cross-sectional shape of the concrete structure. Each of the pair of tie rods 15, 16 is connected between both ends of one angle band 13 and both ends of the other angle band 14, both of which are opposite to each other, and is formed so that it can adjust the dimensions between both of the ends which are opposite to each other by a screw.