We describe a 43-year-old woman who underwent laparoscopic distal pancreatectomy preserving the spleen and splenic vessels for the treatment of insulinoma in the pancreatic body. The patient experienced cold sweats on fasting, received diagnosis of insulinoma, and was referred to our hospital for laparoscopic surgery. Blood biochemistry studies showed low fasting blood glucose of 42 mg/dL, serial immunoreactive insulin of 15.2 microU/mL, and a Fajans index (immunoreactive insulin/blood glucose) of 0.36 (normal <0.30). Contrast-enhanced early-phase computed tomography of the abdomen showed a circular, intensely stained, 1.6-cm-diameter tumor in the pancreatic body close to the main pancreatic duct. A solitary insulinoma of the pancreatic body was diagnosed on the basis of the result of hematologic studies, and diagnostic imaging results. Because of the location of the tumor, we elected to perform distal pancreatectomy preserving the spleen and splenic vessels, rather than enucleation. Insulin and blood glucose levels were monitored during surgery. Before removal of the tumor, insulin levels remained consistently high, never decreasing to less than 10 microU/mL. After surgery, insulin levels decreased rapidly, to less than 5 microU/mL within 30 minutes and subsequently remained at the new low level, leading us to conclude that the entire tumor had been removed. There were no postoperative complications, and the patient was discharged from the hospital on day 7. There was no major intraoperative bleeding other than at the resected surface. The patient was ambulatory soon after the procedure, and had a brief hospital stay therefore, the surgery was judged to have been highly useful in this case.