To provide a lubricant composition which can effectively reduce rattling without increasing sliding noises or excessively raising the rotational torque of a reduction gear and the steering torque of an electric power steering device when used in a reduction gear having a gear and a pinion meshing with each other by rolling contact, and also to provide a reduction gear and an electric power steering device using the same.

The lubricant composition has a consistency of No.2 to No.000 and is formed by compounding a base oil having a kinematic viscosity (40C) of 200-10,000 mm2/S, a thickening agent, and 5-50 mass% cushioning material particles having an average particle diameter of 50-500 m. The reduction gear 19 comprises the lubricant composition and the electric power steering device 1 comprises the reduction gear.