To provide an underground tank structure which contributes to reduction of manufacturing costs.

The underground tank structure is formed of a continuous underground wall 2, a cylindrical side wall 3 having an external peripheral surface thereof abutting on an internal peripheral surface of the continuous underground wall 2, a roof 4 arranged on an upper edge of the side wall 3, and a bottom slab 5 arranged on a lower edge of the side wall 3. The side wall 3, the roof 4, and the bottom slab 5 define an internal space. Herein the sum of the weights of the continuous underground wall 2, the side wall 3, the roof 4, and the bottom slab 5 is set as an underground tank weight, and the underground tank structure is set in a mode in which the sum of the underground tank weight and a skin friction acting on a section of the internal peripheral surface of the continuous underground wall 2, that is lower than the bottom slab 5, is equal to or more than an uplift pressure acting on the bottom slab 5.

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