To enhance the performance of an oil free scroll fluid machine and the cooling performance of each sliding part thereof.

A fixed scroll 2 is fixed to the opening portion of a casing 5, a part of the opening portion which is not covered by the fixed scroll 2 is set as an air duct port 47 for cooling air, and both end portions of a driving shaft 13 are supported by a main bearing 22 equipped on the end wall 20 of the casing 50 and a bearing 14 equipped to the fixed scroll 2. A joint plate 31 is integrally fixed to an end plate 24 of a swing scroll 4 to be spaced from the end plate 24 at a predetermined interval, and a swing bearing 36 equipped at the center portion of the joint plate 13 is supported by a crank portion 28 of the driving shaft 13 so that the joint plate 13 and the swing scroll 4 can make swing motion. A vent hole 37 serving as a flow path for the cooling air is formed in the joint plate to be located on the outer periphery of the swing bearing 36, an air flow plate 51 projecting from the inner wall of the casing 5 to the driving shaft 13 is provided in the vicinity of the side surface of the joint plate 13 at the opposite side to the swing scroll side, and an air discharge port 53 for the cooling air is formed so as to penetrate through the wall of the casing 5 between the outer periphery of the main bearing 22 and the air flow plate 51.