A container refrigeration unit mounted on a container body (1a) includes a casing body (11) partitioning the container into the internal side and the external side thereof. A protruding portion (12) protruding toward the internal side is formed in a lower portion of the casing body (11), and the side stays (50) each extending vertically are mounted on both sides of the rear surface of the protruding portion (12). On the contrary, evaporator frames (40) each located above the protruding portion (12) and extending from the casing body (11) to a top end of the side stay (50) are mounted on both sides of an upper portion of a rear surface in the casing body (11). The bottom tip of the side frame (40) and the top end of the side stay (50) are fixed by a bolt.