Recently, actinomycosis has become rare owing to the frequent use of antibiotics. Most cases of actinomycosis occur in the head and neck region, but the primary parotid gland actinomycosis is very rare. We experienced a case of parotid actinomycosis that occurred after parotid surgery. A 56-year-old man underwent a superficial partial parotidectomy for a left Warthin tumor. One and a half months later, he complained of a diffuse hard mass in the left parotid gland. It was increasing in size with an unclear border and board-like swelling. The skin surface had a peachblow appearance. After diagnosis of the actinomycosis, treatment consisted of 1.5 months of intravenous penicillin (SBT/ABPC: 12g/day), followed by 9 months of oral penicillin (AMPC 1500mg/day). The patient has shown no sign of recurrence. A possible route of infection could be that actinomyces from the dental surfaces was carried into the parotid gland through Stensen's duct, and the actinomycosis was caused by parotid surgery. Furthermore, it may be promoted by diabetes.