NOVELTY - Producing (M1) fermented mushroom mycelial culture, involves cultivating mycelium of mushroom in a culture medium containing excess amount of saccharide than the amount consumed for the growth of mycelium of mushroom, for a predetermined period, and mixing mushroom mycelial culture with microorganisms capable of carrying out fermentation.    USE - (M1) is useful for producing fermented mushroom mycelial culture. (M1) is useful for preparing fermented food (claimed). The fermented product of (M1) is useful for activating cell such as natural killer cell, associated with immune function. The fermented product is useful for stimulating immune response, and useful as anti-oxidant or anti-cancer agent.    ADVANTAGE - (M1) enables production of mushroom mycelial culture (claimed), which is suitable as a raw material of foodstuffs for the consumer in whom the saccharide ingestion is not preferable. The fermenting microorganisms used in the method suppress the proliferation of various microorganisms, and thus provide foodstuff material excellent in flavor. The fermented product exhibits immune stimulation activity, anti-mutagenic activity, hyperlipidemia improving effect, cell activating effect, anti-atopic effect, anti-oxidant effect, intestinal regulating effect, and anti-cancer effect.    DETAILED DESCRIPTION - Producing (M1) fermented mushroom mycelial culture, involves cultivating mycelium of mushroom in a culture medium containing excess amount of saccharide than the amount consumed for the growth of mycelium of mushroom, for a predetermined period, and mixing mushroom mycelial culture with microorganisms capable of carrying out fermentation, where the remaining sugar is degraded and the saccharide content is reduced, during the fermentation of mushroom mycelial culture.    INDEPENDENT CLAIMS are also included for:    (1) fermented mushroom mycelial culture obtained by (M1), or by fermenting mushroom mycelial culture by mixing mushroom mycelial culture and microorganisms capable of carrying out fermentation; and    (2) fermented food obtained by processing fermented mushroom mycelial culture obtained by (M1).    DESCRIPTION OF DRAWING(S) - The figure is a graph representing the antioxidation ability (active oxygen elimination ability) of fermented mushroom mycelial culture. (Drawing includes non-English language text).