A radio frequency coil unit includes a chassis which has a tubiform inner cylinder, a plurality of flanges arranged apart from each other, each of the plurality of flanges provided in a state of protruding outwards from the inner cylinder while in contact with a whole outer circumference surface of the inner cylinder, and a tubiform external cylinder in which each of the plurality of flanges is provided in a state of contacting an inner surface thereof, wherein the chassis forms a flow path of cooling air as a space surrounded by the inner cylinder, the plurality of flanges and the external cylinder, and a radio frequency coil which is mounted on the inner cylinder or the external cylinder to be positioned in the space surrounded by the inner cylinder, the plurality flanges and the external cylinder.