The present invention provides a method for producing a C-glycoside derivative, which can produce the C-glycoside derivative at a high yield and at a low cost, which conforms to environmental protection, and which is applicable industrially. The C-glycoside derivative is useful for treating and preventing diabetes such as insulin-dependent diabetes (type 1 diabetes), non-insulin-dependent diabetes (type 2 diabetes) and the like and various diabetes-related diseases including insulin-resistant diseases and obesity.