PURPOSE: To improve abrasion resistance of a sliding face and attain light weight of sliding parts by forming a roller and a vane of aluminum alloys or ceramic reinforced aluminum alloys, and applying a hard alumite coat on the surface of one aluminum alloy.

CONSTITUTION: A rotary compression element 1 is formed of a cylinder 2, a shaft 3, a roller 5 rotated inside the cylinder by the eccentric part 4 of the shaft 3, a vane 8 in contact with the roller 5 so as to partition the inside of the cylinder 2 into a high pressure chamber 6 and a low pressure chamber 7, and an upper bearing part 9 and a lower bearing part 10 for supporting the shaft 3 rotatably, closing up the opening of the cylinder 2. The roller 5 is formed of an aluminum alloy of the coefficient of linear expansion 10W18×10-6 or a ceramic reinforced aluminum alloy, and the vane 8 is formed of iron material, an aluminum alloy of the coefficient of linear expansion 10W18×10-6, or a ceramic reinforced aluminum alloy. The roller 5 is further provided with a hard alumite coat 11 applied to the surface of the aluminum alloy.