The invention provides a lube base oil other than silicone oil having a kinematic viscosity of 12 mm.sup.2/s or below at 40.degree. C., exhibiting, in Noack test (250.degree. C., 1 hr), an evaporation loss of 30 mass % or below and/or a flash point of 200.degree. C. or higher, and exhibiting an aniline point of 60.degree. C. or higher. There is also provides a lubricating oil composition comprising the lube base oil mixed with at least one additive selected from the group consisting of an antioxidant, a viscosity index improver, a detergent dispersant, a friction reducing agent, a metal inactivator, a pour point depressant, an abrasion resisting agent, a defoamer, and an extreme-pressure additive. The lube base oil and the lubricating oil composition realize reduction of evaporation loss despite being of low viscosity and excellent compatibility with organic materials.