A new and distinct variety of mushroom, named `Grifon 120`, is described, which mushroom is characterized by its cap with thick flesh and delicious-looking whitish undersurface, good qualitative character and appearance, good keeping quality and storage life and delicious tasting. The mushroom can be cultivated by gathering and repeated breeding of fungal strains having dominant traits and is exquisite in stability, reproducibility and uniformity when being produced.