A head drum assembly for use in a video cassette recorder includes a stationary drum, a rotary shaft rotatably fitted into the stationary drum, a rotary drum closely fitted onto the rotary shaft, a lower bearing fitted into a lower portion of the stationary drum and an upper bearing fitted into an upper portion of the stationary drum. Herein, the upper bearing includes a top surface facing the rotary drum and an inner peripheral surface, facing the rotary shaft. The top surface is provided with a plurality of building-up grooves for retaining an oil for lubricating the upper bearing and the inner peripheral surface is provided with an oil guiding groove for guiding the oil retained on the inner peripheral surface onto the building-up groove of the top surface during rotation of the rotary shaft.