The purpose of the present invention is to provide a method of preparing an Inonotus obliquus-fermented red ginseng vinegar, which improves saponin component of conventional red ginseng, enables betaglucan contained in Inonotus obliquus to be contained in red ginseng, prepares vinegar having reduced unique repulsive smell of red ginseng, and prepares a red ginseng vinegar with improved red ginseng functionality. A method of preparing an Inonotus obliquus-fermented red ginseng vinegar according to the present invention comprises: (1) a step of milling dried Inonotus obliquus to a particle size of 1 &mum to 10 &mum (2) a step of drying salt-free Cheonggukjang (natural fermented soybean), and milling the dried salt-free Cheonggukjang to a particle size of 100 &mum to 300 &mum (3) a step of mixing the salt-free Cheonggukjang powder from the step (1) with purified water at a weight ratio of 1:1 (4) a step of fermenting the mixture from the step (3) at a temperature of 30 to 40°C for 2 to 5 days (5) a step of filtering the fermented completed material from the step (4) to obtain a Cheonggukjang fermented liquor (6) a step of mixing the Inonotus obliquus powder from the step (1) with the Cheonggukjang fermented liquor from the step (5) at a volume ratio of 20 : 1 to 20 : 10 to ferment the mixture at a temperature of 25 to 50°C for 3 to 10 days (7) a step of preparing a red ginseng powder having a particle size of 0.1 to 1 &mum from dried red ginseng (8) a step of mixing the material from the step (6) with the material from the step (7) at a volume ratio of 1 : 1 to 1 : 3 to ferment the mixture at a temperature of 20 to 45°C for 3 to 7 days (9) a step of drying the material from the step (8) to obtain a red ginseng powder fermented with Inonotus obliquus (10) a step of preparing a fermented vinegar for a medium or brewed vinegar for a medium (11) a step of mixing the vinegar for medium from the step (10) with the material from the step (9) at a weight ratio of 1 kg
