Supercharger

A supercharger (10) includes a centrifugal compressor (22) having an impeller (24), a rotational shaft (26) coupled to the impeller (24), a motor (20) having a stator (14) and a rotor (18) housed in a casing (12), and a journal air bearing (28a) supporting the rotational shaft (26). The journal air bearing (28a) includes a hollow cylindrical member (36) having an inner space (40) therein and a heat transfer member (48) fitted in the inner space (40). The heat transfer member (48) is made of a material which is less rigid and has a greater coefficient of thermal conductivity than the hollow cylindrical member (36). The impeller (24) radiates heat transferred through the heat transfer member (48) into ambient air.