Background/Aims: Detailed information on the age- and sex-specific relationships between diabetes and Alzheimer’s disease (AD) is scarce. This study aims to prospectively investigate the age- and sex-specific incidence density and relative hazards of AD in relation to diabetes. Methods: A total of 615,529 diabetic patients and 614,871 age- and sex-matched random controls were linked to the claim data from 2000–2008 to identify the first occurrence of a primary or secondary diagnosis of AD. Incidence density was calculated under the Poisson assumption. We also assessed the age- and sex-specific risk of AD in relation to diabetes with the Cox proportional hazards regression model. Results: Over nearly 9 years of follow-up, a total of 4,615 diabetic subjects developed AD, representing a cumulative incidence rate of 0.75% (n = 3,873; 0.63% in controls). The overall incidence densities of AD for diabetic men and women, respectively, were 0.82 and 1.15 per 1,000 person-years, which were higher than those for control men and women (0.63 and 0.89 per 1,000 person-years, respectively). Diabetic patients had a significantly higher hazard ratio (HR) of AD [1.45, 95% confidence interval (CI) 1.38–1.52]. Diabetic women ≥65 years had a higher HR (1.52, 95% CI 1.42–1.62) than diabetic women <65 years (1.34, 95% CI 1.15–1.56). Conclusion: Diabetes may increase the risk of AD in both sexes and in all ages. A higher HR of AD was especially notable in older diabetic women.