To provide a method for improving earth and sand which can easily granulate earth and sand and stabilize them.

An aqueous solution 14a of a polymer-based improver 10 is obtained by stirring and mixing the polymer-based improver 10 with water 11 by using a stirrer 13. Concretely, the polymer-based improver 10 of not more than 0.5 by weight is mixed with water 11 of 100 by weight. This is sprinkled on not yet improved soil 19 and then it is stirred by using digging vanes 21 for improvement. Next, a powdery lime-based soil improver is sprinkled on the earth and sand followed by mixing and stirring again. In the first process, fine earth and sand particles are granulated into sand-like state. In the second step, the earth and sand come to be in the state that the earth and sand are wafered with the powdery lime-based sand improver whereby the improved earth and sand become so stable that they do not easily collapse even when there is an external effect such as rain.