To provide a lubricant composition which can be suitably used for reducing gear noises by buffer particles, sufficiently maintaining effect for reducing noise in a car room and further reducing the steering torque of an electric power steering device than that in the present condition, a decelerator giving small noise and sufficiently reducing the steering torque of the electric power steering device by using the lubricant composition, and the electric power steering device by using the decelerator.

The lubricant composition containing at least one of (1) an oil membrane-forming component which forms the oil membrane by adsorbing a lubrication oil on the surface of the buffer particles in the lubricant composition and (2) a solid lubricant, the decelerator 50 filled with the lubricant composition and the electric power steering device assembled with the decelerator are provided.