To provide a storage infiltration tank for storing a large amount of temporarily collected rainwater underground, and in which the rainwater is slowly infiltrated into the ground gradually, which facilitates prompt infiltration of stored water, reduces additional amount of investment for new plant and equipment, and can be easily constructed.

The storage infiltration tank 1 is buried with crushed stones 101 in a row under a narrow strip of land in such a manner that a recessed side ditchs 3 are arranged with the bottom 31 put upside down in series on a bottom slab 2 having an opening 21 lengthwise in an excavated section 100 so as to form an internal space for storing rainwater and also the sorrounding of the side ditch is filled with crushed stones 101. An artificial base 102 is constructed on the bottom 31 of the side ditch 3.

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