To provide a sand separation washing device capable of separating only a sand component by efficiently washing and separating a foreign matter contained in sunk sand raised from a sand sedimentation pond.

This sand separation/washing device is provided with an upper solid/liquid separation washing tank 1 introduced with contaminated sand mixing water; and a lower stirring washing tank 2 installed beneath the upper solid/liquid separation washing tank 1. The upper solid/liquid separation washing tank 1 is provided with a cylindrical upper tank body 3 for generating a rotation flow descending along a peripheral wall by making the contaminated sand mixing water flow-in in a tangent direction; an ascending flow pipe 4 vertically provided near a center of the upper tank body 3 so as to be communicated with the lower stirring washing tank 2, forming a flowing-in port 41 near a bottom part of the upper tank body 3, introducing the rotation flow from the flowing-in port 41 as the ascending flow and making it flow out to the outside of the upper tank body 3; and a feeding screw 5 arranged at the bottom part of the upper tank body 3 and feeding the settled contaminated sand to the flowing-in port 41 of the ascending flow pipe 4.