Purpose: This study was to examine the relation between diabetes and cognitive function in older adults. Methods: Eighty community-dwelling patients with diabetes and 506 subjects without diabetes were studied with cognitive function test. Cognitive function was measured by Full-scale IQ, Basic IQ, Executive IQ, Attention Function Index, Working Memory Index, Language Function Index, Visuospatial Function Index, Memory Function Index, and MMSE-K1. Results: In model controlling for education, the diabetic group showed significantly lower scores than the non-diabetic group in in Full-scale IQ (p=.012), Basic IQ (p=.034), Executive IQ (p=.014), Attention Function Index (p=.002), Working Memory Index (p=.037), and Memory Function Index (p=.043). The diabetic and non-diabetic groups that were matched for gender, age, and education showed similar differences in 7 out of 9 cognitive measures. The impairments of Full-scale IQ and Memory Function Index in the diabetic group were, respectively, 2.7 and 2.8 times greater than that in the diabetic group. Conclusion: These results showed that diabetes should be considered to a factor of cognitive impairment in older adults.