The lubricating base oil of the invention has a urea adduct value of not greater than 4 % by mass, a kinematic viscosity at 40°C of 25-50 mm 2 /s, a viscosity index of 140 or greater, a CCS viscosity at -35°C of not greater than 15,000 mPa·s and a flash point of 250°C or higher. The method for producing a lubricating base oil of the invention comprises a step of hydrocracking/hydroisomerizing a feedstock oil containing normal paraffins so as to obtain a treated product having an urea adduct value of not greater than 4 % by mass, a kinematic viscosity at 40°C of 25-50 mm 2 /s, a viscosity index of 140 or greater, a CCS viscosity at -35°C of not greater than 15,000 mPa·s and a flash point of 250°C or higher. The lubricating oil composition of the invention comprises the lubricating base oil of the invention.