A method for mass production of high quality mushroom mycelia through the second culturing of mushroom mycelia comprises: a first step that is a medium material preparing step of preparing grains as medium materials a second step that is a medium production step of inserting the grains into a predetermined sized plastic bag to facilitate second culturing, sealing the plastic bag, and sterilizing the grains in the plastic bag to prevent various germs from being multiplied, thereby producing a medium a third step that is a seed inoculating step of inoculating the medium with prepared mushroom seeds after moving the produced medium to an aseptic room a fourth step that is a first culturing step of primarily culturing the mushroom seed-inoculated medium at a predetermined temperature for a predetermined period of time a fifth step that is a second culturing preparation step of finely breaking the medium which has been primarily cultured and in which a predetermined amount of mushroom mycelia is contained, thereby widening a space between media within the plastic bag to improve a growing environment of the mushroom mycelia such that the mushroom mycelia are grown and filled in the widened space between the media a sixth step that is a second culturing step of performing a second culturing process by shining a light of a predetermined brightness on the mushroom mycelia to activate the mushroom mycelia and a mushroom mycelium drying step of drying the culturing-completed mushroom mycelia such that the mushroom mycelia have a predetermined level or less of moisture. A method for mass production of high quality mushroom mycelia through second culturing of mushroom mycelia according to the present invention has enabled the mass production, has an effect of increasing production yield, and is capable of mass-producing mycelia with excellent functionality per mushroom such that the mycelia can be utilized as materials for food additives, cosmetics, and medicines and medical sup
