Abstract: In a supercharging device for an internal combustion engine including an air compressor, a bearing holder, and a planetary gear type of speed increasing gear device with an internal gear, a pair of pinion gears, and a sun gear, a oil channel guiding lubricating oil to the plain bearings to form oil film damper is provided in the bearing holder. In the bearing holder located between the pinion gears, an oil guide means for directing the lubricating oil, splashed from the pinion gears toward the oil guides, in the direction of the sun gear, is provided. A thrust washer can be arranged between the plain bearings to receive the thrust force of the impeller shaft.