The present invention relates to a dark vinegar preparation method including: a hard-boiled rice preparation step in which 100 parts by weight of water are mixed with 30 to 35 parts by weight of brown rice and 30 to 35 parts by weight of glutinous rice, and then the mixture is heated after seven to eight hours a crude liquor preparation step in which 100 parts by weight of the hard-boiled rice are mixed with 90 to 110 parts by weight of malt and 190 to 210 parts by weight of water, and then the mixture is fermented for 30 to 50 days at 10 to 15°C a step in which 100 parts by weight of the crude liquor are mixed with 40 to 45 parts by weight of one or more selected from bean sprouts, black soybean, black bean, corn, sorghum, brown rice, Poria cocos Wolf, acanthopanax, schizandra, cyperus, black cumin, motherwort, foxglove, cornus fruit, white woodland peony, angelica root, cnidium, milk vetch root, white atractylis, licorice, red ginseng, Dioscorea rhizoma, artemisia herb, dried tangerine peel, amomum fruit, ginger, cinnamon, mint, achyranthes, apricot, Japanese plum, strawberry, jujube, and pine needle, and the mixture is subjected to high-temperature fermentation for 48 to 60 hours at 40 to 60°C a step in which the crude liquor fermented at the high temperature is subjected to primary aging for 80 to 90 days at 20 to 35°C a step in which 0.5 to 3.0 parts by weight of rice straw is put into 100 parts by weight of the crude liquor subjected to the primary aging, and then the mixture is stored for five to seven months at 5 to 15°C a step in which the rice straw is removed from the stored crude liquor and vinegar is prepared by bacteria being activated for five to seven months at 20 to 40°C a step in which 100 parts by weight of the bacteria-activated vinegar are mixed with 20 to 30 parts by weight of a mulberry extract and a step in which dark vinegar is prepared by the mulberry extract-mixed vinegar being subjected to secondary aging for five to seven
