Provided are both a grease composition for an electric power steering device and an electric power steering device. The grease composition can keep a sufficiently low coefficient of friction in a sliding area between a steel and a resin over a long period, is less susceptible to being removed from the sliding area, does not cause break down of an oil film, and thus can minimize the occurrence of stick-slips. A grease composition for an electric power steering device, containing a synthetic hydrocarbon oil which exhibits a density of 0.75 to 0.95 g/cm3 at 15° C., a saturated aliphatic amide compound, boron nitride, a glycerin fatty acid partial ester, and a metal soap-based thickener; and an electric power steering device using the grease composition.