A method of simultaneously manufacturing high quality naphthenic base oil having a low viscosity and heavy base oil having a high viscosity using a single catalyst system comprising a hydrotreating catalyst, a dewaxing catalyst and a hydrofinishing catalyst, the method comprising: (a) subjecting atmospheric residue to fluid catalytic cracking and separating the cracked products to obtain light cycle oil or/and slurry oil thereby producing the feedstock for naphthenic base oil; (b) subjecting a vacuum residue or a mixture comprising atmospheric residue and vacuum residue to solvent deasphalting thereby producing deasphalted oil, and separating appropriately the deasphalted oil thereby preparing the feedstock for heavy base oil; (c) sequentially or simultaneously hydrotreating the feedstock for naphthenic base oil produced in step (a) and the feedstock for heavy base oil prepared in step (b) under conditions including a reaction temperature of 300-410°C, a reaction pressure of 30-220 kg/cm 2, and a liquid hourly space velocity of 0.1-3.0 h -1, and a volume ratio of hydrogen to feedstock of 500-3000 Nm 3 /m 3, using the hydrotreating catalyst comprising one or more components selected from among Groups 6 and 8 to 10 elements of the periodic table, thus obtaining a hydrotreated oil fraction; (d) catalytically dewaxing the hydrotreated oil fraction obtained at step (c) under conditions including a reaction temperature of 250-410°C, a reaction pressure of 30-200 kg/cm 2, and a liquid hourly space velocity of 0.1-3.0 h -1, and a volume ratio of hydrogen to feedstock of 150-1000 Nm 3 /m 3, using the dewaxing catalyst comprising one or more supports selected from among a molecular sieve, alumina, and silica-alumina, and one or more metals selected from among Groups 2, 6, 9 and 10 elements of the periodic table, thus obtaining a dewaxed oil fraction; (e) hydrofinishing the dewaxed oil fraction obtained at step (d) under conditions including a reaction temperature of 150-300°C, a reaction pressure of 30- 200 kg/cm 2, and a liquid hourly space velocity of 0.1-3.0 h -1, and a ratio of hydrogen to the supplied oil fraction of 300-1500 Nm 3 /m 3, using the hydrofinishing catalyst comprising one or more supports selected from among silica, alumina, silica-alumina, titania, zirconia, and zeolite, and one or more metals selected from among Groups 6, 8, 9, 10 and 11 elements of the periodic table, thus obtaining a hydrofinished oil fraction; and (f) fractionating the hydrofinished oil fraction obtained in step (e) according to a viscosity grade. (a) subjecting atmospheric residue to fluid catalytic cracking and separating the cracked products to obtain light cycle oil or/and slurry oil thereby producing the feedstock for naphthenic base oil; (b) subjecting a vacuum residue or a mixture comprising atmospheric residue and vacuum residue to solvent deasphalting thereby producing deasphalted oil, and separating appropriately the deasphalted oil thereby preparing the feedstock for heavy base oil; (c) sequentially or simultaneously hydrotreating the feedstock for naphthenic base oil produced in step (a) and the feedstock for heavy base oil prepared in step (b) under conditions including a reaction temperature of 300-410°C, a reaction pressure of 30-220 kg/cm 2, and a liquid hourly space velocity of 0.1-3.0 h -1, and a volume ratio of hydrogen to feedstock of 500-3000 Nm 3 /m 3, using the hydrotreating catalyst comprising one or more components selected from among Groups 6 and 8 to 10 elements of the periodic table, thus obtaining a hydrotreated oil fraction; (d) catalytically dewaxing the hydrotreated oil fraction obtained at step (c) under conditions including a reaction temperature of 250-410°C, a reaction pressure of 30-200 kg/cm 2, and a liquid hourly space velocity of 0.1-3.0 h -1, and a volume ratio of hydrogen to feedstock of 150-1000 Nm 3 /m 3, using the dewaxing catalyst comprising one or more supports selected from among a molecular sieve, alumina, and silica-alumina, and one or more metals selected from among Groups 2, 6, 9 and 10 elements of the periodic table, thus obtaining a dewaxed oil fraction; (e) hydrofinishing the dewaxed oil fraction obtained at step (d) under conditions including a reaction temperature of 150-300°C, a reaction pressure of 30- 200 kg/cm 2, and a liquid hourly space velocity of 0.1-3.0 h -1, and a ratio of hydrogen to the supplied oil fraction of 300-1500 Nm 3 /m 3, using the hydrofinishing catalyst comprising one or more supports selected from among silica, alumina, silica-alumina, titania, zirconia, and zeolite, and one or more metals selected from among Groups 6, 8, 9, 10 and 11 elements of the periodic table, thus obtaining a hydrofinished oil fraction; and (f) fractionating the hydrofinished oil fraction obtained in step (e) according to a viscosity grade.