This study is developed a self-propelled Welsh onion harvester to increase farm household income by mechanizing the labor-intensive Welsh onion harvesting operation. In order to evaluate the performance of the developed harvester, the work capacity, damage rate, and harvest rate are investigated for three traveling speed levels (7.3cm/s, 12.3cm/s, 19cm/s). Work capacity is increased proportionally to 1.8a/hr, 3.1a/hr, and 4.9a/hr, respectively, as the traveling speed increased. And the damage rate also is increased in proportion to the traveling speed, and under the same conditions, it is increased proportionally to 2.9%, 3.9%, and 4.4%, respectively. The harvest rate is 100% at all speeds of the Welsh onion harvester. The developed harvester is expected to greatly contribute to improving the cultivation environment of Welsh onion by enabling mechanization of the harvesting operation with the largest amount of labor during the Welsh onion production.