Introduction: The Japan Stroke Data Bank (JSDB) is a 20-year long ongoing hospital-based multicenter prospective registry of hospitalized patients with acute stroke/TIA based on a web database from 130 stroke centers distributed evenly over Japan. Hypothesis: Secular changes in the severity and functional outcome of stroke patients would be clarified by long-lasting hospital-based registries. Methods: Patients registered in JSDB within 7 days after stroke onset from Jan 2000 through Dec 2019 were studied. The initial severity was assessed by the NIHSS for ischemic stroke (IS) and intracerebral hemorrhage (ICH) and by the WFNS grading for subarachnoid hemorrhage (SAH). Outcomes at hospital discharge was assessed by the mRS. Results: Of a total 183,082 stroke patients, 135,268 (women in 39.8%) developed IS, 36,014 (women in 42.7%) developed ICH, and 11,800 (women in 67.2%) developed SAH. Median ages at onset increased and the NIHSS and WFNS scores decreased after multivariable-adjustment in all three stroke types. Patients with favorable outcome, corresponding to the mRS 0-2, significantly increased after age-adjustment in all three IS subtypes, remained increasing after further adjustment by NIHSS and stroke history only in cardioembolic stroke (OR 1.014, 95% CI 1.008-1.020, per year), and no longer increased after further adjustment by reperfusion therapy in any subtypes. Both the frequencies of unfavorable outcome, corresponding to the mRS 5-6, and in-hospital death, significantly decreased in cardioembolic stroke (OR 0.974, 95% CI 0.968-0.980) and large-artery atherosclerosis (OR 0.975, 95% CI 0.967-0.982, both for unfavorable outcome) after multivariable-adjustment. In ICH and SAH, favorable outcome significantly decreased after multivariable-adjustment, except for SAH in men. Both the frequencies of unfavorable outcome and death after SAH significantly decreased, but those after ICH were not. These findings were generally common to both sexes when separately analyzed. Conclusions: Short-term functional outcome improved in IS patients during the past 20 years presumably partly due to development of acute reperfusion therapy. The outcome of hemorrhagic stroke patients did not clearly show the improvement during the same duration.