A method of mass producing potato seedlings, involves collecting growing points of seed potatoes and culturing the growing points in a liquid or solid medium; introducing in vitro plantlets obtained from the culture of the growing points to solid culture; and removing the in vitro plantlets from the solid culture, and planting through stem cutting and acclimatizing the in vitro plantlets in deep flow culture, in which a nutrient solution is circulating. Upon planting in hydroponic facilities, such potato seedlings have high adaptability to the external environment and thus rapidly, uniformly generate roots in a short time. The rapid root anchoring prevents planted seedlings from withering, leading to death, growing poorly, and the like. The direct planting of in vitro plantlets through stem cutting without a separate acclimatization process shortens the overall production period of potato seedlings by omitting the acclimatization process.