Since the first Korean button mushroom ‘Sae-Ah’ developed in 2010, most farmers had wanted to cultivate a new variety. A new variety, ‘SaeJeong’, was developed in 2011, but this variety was difficult to cultivate in mushroom farm. To solve the variety problem, a new variety ‘Sae-do’ was developed in 2012. The variety, ‘Sad-do’, was made by crossing hetrokaryon A175 and homokaryon ASI1346-15 selected by genetic analysis. The heterokaryon A175 is crossed line between ASI1038-211 and ASI1346-20. The mycelium of ‘Saedo’ on CDA (compost dextrose agar) grew well at 25°C. The optimum pin-heading temperature of it was 13-15°C and optimum growing temperature was 13-20°C. Earliness (days required from casing to first harvesting) was 2 days shorter than control ‘Saejeong’. Even though the diameter of mature cap and the length of stipe were shorter than a control, the individual weight of fruiting body was heavier because of thick pileus and stipe. Therefore, the yield was increased by 1.89 times than control and the hardness of pileus was stronger. The field experiment of ‘Saedo’ variety has been started since 2013. Most farmers evaluated that the variety has good compost colonization and cap shape, and high yield in harvesting. For that reason, ‘Saedo’ has occupied half of the of distribution rate of Korean varieties. Also distribution rate of Korean varieties was increased from 26.1% in 2014 to 37% in 2015.