Abstract: A small-sized, efficient compressor has a compressed air tank, a first housing provided with a shaft bore, a rotating shaft, an orbiter, a second housing, a rotation restrainer and a circular vane. The orbiter is provided at a lower portion thereof with a cam shaft hole to engage with the cam shaft portion of the rotating shaft without friction, and is adapted to form a ring-shaped operating portion above the orbiter to form a circular space. The second housing is attached to the first housing and forms a second circular space offset from the circular space. The circular vane is formed in the second housing to form a ring-shaped compression chamber within the operating portion of the orbiter. Air is compressed and discharged through a discharge hole of the circular vane to generate a large amount of highly compressed air.