Objective: Although bariatric surgery including diverse type gastrectomy has recently emerged as a potentially useful treatment for type 2 diabetes, it is not clear until now whether gastrectomy can give beneficial effect on glucose metabolism or not. Therefore, in this study, we investigated changes of glucose levels according to the subtotal or total gastrectomy in type 2 diabetic and non-diabetic patients. Methods: From Jan 2010 to May 2014,77 diabetic and 89 non-diabetic patients who underwent gastrectomy at Chon-buk national university hospital, South Korea were included and we compared the fasting plasma glucose levels, HbA1c, and anti-diabetic management between before and after gastrectomy. Results: After gastrectomy, 99 patients (60.7%) showed reduced FPG levels at the point of 1 year, and 89 patients (50.9%) showed reduced FPG at the point of 3 years, irrespective of diabetes. Among 77 diabetic patients, the decrease of FPG was observed in 55 patients (71.4%) and 31 patients (40.3%) at 1 year and 3 years after gastrectomy, respectively. Among 89 non-diabetic patients, at the point 1 year and 3 years after gastrectomy, 44 patients (51.2%) and 58 patients(67.4%) showed reduced FPG levels. In the patients of reduced FPG after gastrectomy, average values of decreased FPG of diabetic patients and non-diabetic patients are as follows : -30.3 ± 31.4 vs -41.8 ± 38.7 after 1 year, - 43.5 ± 45.0 vs -35.5 ± 28.1 after 3 years. There were no statistically significant differences according to the diabetes and time passage (P > 0.05). On the contrary, after gastrectomy, FPG levels of 28.6% and 59.7% diabetic patients and 48.8% and 32.6% non-diabetic patients were increased after 1 year and 3 years, respectively. Conclusion: Gastrectomy did not show consistent results in the glucose reduction in diabetic or non-diabetic patients, and over around half of patients, FPG levels were rather increased after gastrectomy. Moreover, glucose level can be increased in diabetic and non-diabetic patients although gastrectomy in this study were performed due to gastric malignancy treatment. Therefore, bariatric surgery including gastrectomy needs to be performed with care, and OGTT may be necessary to assess or predict glucose state after gastrectomy.