A compression mechanism that can suppress generation of galling and seizure is provided. The compression mechanism includes a bush 60 including a first sliding surface 61 sliding with an inner surface 45a of a bush hole 45 and a second sliding surface 63 sliding with a side surface 52a of a blade of a piston, and includes at least one of a first bulge 62 formed on one of the first sliding surface 61 and the inner surface 45a such that a gap X between the first sliding surface 61 and the inner surface 45a gradually decreases toward a direction in which lubricant Y is drawn between the first sliding surface 61 and the inner surface 45a along with rocking of the bush 60, and a second bulge 64 formed on the second sliding surface 63 such that the gap X between the second sliding surface 63 and the side surface 52a gradually decreases toward a direction in which the lubricant Y is drawn between the second sliding surface 63 and the side surface 52a along with forward and backward movement of the blade.