Abstract: A rotary damper includes a sealed cylindrical housing containing viscous oil, a driven shaft rotatably supported within the housing, and a plurality of rotors and spacers arranged alternately and disposed upon a portion of the driven shaft extending in the axial direction of the housing. The rotors are held rotatably in unison with the driven shaft. The spacers are secured to the housing so as to permit the driven shaft to be rotated relative to the spacers. The rotors and spacers are formed with respective air-purging notches communicating with gaps defined between the rotors and the spacers whereby the air can be eliminated from such gaps and the viscous oil disposed within such gaps in order to provide the damper with the desired damping efficiency.