Disclosed are a process suited to large scale synthesis with high yield for producing oseltamivir phosphate, in which a preparation of oseltamivir phosphate which is highly safe as a pharmaceutical product can be produced, and an intermediate compound for producing oseltamivir phosphate. In this production process, an intermediate compound represented by general formula (V) is synthesized by employing Michael reaction/Michael reaction/Horner-Wadsworth-Emmons reaction, and oseltamivir phosphate is produced by converting the substituent groups in this intermediate compound.