To obtain a lubricating oil containing solid particles dispersed in high dispersibility and free from the problems of precipitation, deposition, etc., in a hydrodynamic pressure generating part of a hydrodynamic lubrication bearing without lowering the characteristics of a base oil by dispersing porous inorganic particles in a base oil.

The objective lubricating oil is produced by dispersing (A) porous inorganic particles in (B) a base oil. A mineral oil, a synthetic oil, etc., is used as the component B owing to the low volatility and small viscosity, surface tension and frictional coefficient and concrete examples of the oil are ester-type mineral oil, ether-type mineral oil, fluorine-based synthetic oil, etc. The component A acts as a friction decreasing agent in the lubricating oil and is preferably porous quartz bead, porous glass bead, etc. The difference between the apparent specific gravity of the component A and the specific gravity of the component B is preferably within ±20%, more preferably within ±5%, further preferably both specific gravity values are nearly equal to each other.