To provide a cement-based improver hardly permitting elution of chromium (VI), and a method for improving earth and sand by granulating earth and sand using the same.

The earth and sand improver 20 contains a chelate of not less than 1 in weight mixing ratio based on a cement of 100. Water 1 is added to the earth and sand improver 20 followed by stirring, and further a polymer-based earth and sand improver 10 is added followed by stirring and mixing. The obtained aqueous solution is sprinkled on not yet improved soil 19 from a nozzle by means of a pump 16 and the soil is mixed by stirring vanes of a cultivator, or the like. The sprinkling of the aqueous solution is conducted to the extent that the water content of the improved earth and sand does not exceed a plasticizing criterion. The obtained improved earth and sand show high drainage to enable adjustment of flow of rain water and improvement of the environment of the ground surface. When a blind sump by using the improved earth and sand layer is arranged in the cultivated base ground or the like, even if the function is lost, it can easily be recovered by repeated improvement though such recovery is impossible in the prior pipe style. Chromium (VI) contained in the cement hardly elutes to the environment since it is chelated by a chelating agent and the content of the detected chromium (VI) does not exceed the environmental criterion of 0.05 mg/l and the improved earth and sand are very safe.