Preparing the larval artificial diet of Euscepes postfasciatus involves two procedures: pre-processing of diet ingredients, and mixing and heating, both of which are complicated. To simplify the diet preparation, we compared the survival and development of E. postfasciatus among three versions of diet: the previous version (diet A), diet B in which three ingredients (dried sweet potato, vitamin mixture and salt mixture) were replaced by ready-processed commercial products without modifying the mixing and heating process, and diet C in which the mixing and heating were simplified using the same ingredients as for diet B. For diet B, the survival rate was higher and the development time was shorter than for diet A, indicating that replacing the ingredients favorably affects the survival and development of insects. The survival rate with diet C was between and did not differ significantly from diets A and B. Development with diet C was longer than with diet B, but did not differ significantly from that with diet A. These results indicate that survival and development with the diet prepared by a simple method is comparable to with the previous diet.