PURPOSE: To make it possible to clean the sand in a sand pit and to reutilize the sand at a low cost.

CONSTITUTION: This sand washing device has a supply conveyor 1 which supplies the sand required to be treated, a primary screen 2 which sieves the sand supplied from this supply conveyor 1 and sorts the sand of a prescribed grain size range, a wet process classifying machine 6 which washes and classifies the sand sorted by this secondary screen 2, a transfer conveyor 7 which transfers the sand washed by this wet process classifying machine 6 and a secondary screen 8 which is disposed with a high-pressure water nozzle 14 and executes secondary washing and draining of the sand supplied from this transfer conveyor 7. Further, the sand washing device is composed of a mixer 16 which sprays a disinfecting liquid to the sand subjected to the secondary washing and a return conveyor 19 which returns the treated sand.