To be able to connect and mount a rack mount device having a rack loaded device loaded thereon to a rack easily, and to be able to release and detach the rack mount device easily from the outside of the rack. The rack mount device has a pair of mount kits for holding the rack loaded device arranged to oppose to each other, which are detachably connected to four mount angles configuring the rack. Each mount kit is configured with a front mount and a rear mount, which are freely slidable with respect to each other in the longitudinal directions thereof. A kit connecting mechanisms for connecting each mount kit to the mount angles are provided to both ends of the mount kits, respectively. A connection releasing mechanism for releasing the connection between the mount kits and the mount angles is provided to each of the kit connecting mechanisms.