To shorten a construction period by facilitating the installation of tanks of various sizes and dispensing with a curing period of concrete for being poured in a base frame and a support.

In this method wherein the tank for storing an oil liquid is buried in a hole made by excavating the ground, the preworked reinforced-concrete base frame 10 with a U-shaped appearance, which comprises a base member 11 and two support members 12, is provided; the hole for burying the tank T is excavated in the ground; at least the pair of base frames 10 are arranged in parallel in the hole; a base reinforcement 30 is arranged between the opposed base members 11; a pillow frame 20 is placed on the base member 11; a base bed is formed by pouring the concrete on the base reinforcement 30; the tank T is placed and fixed on the pillow frame 20; the hole is backfilled; and a concrete pavement is formed on the ground surface.