A motherboard module adapted for connecting pluggably to a case includes a tray, a motherboard, a hard disk cage, and at least one hard disk drive. The tray has a bottom board, a plurality of fixing portions, and a front board. The front board is disposed at a side of the bottom board. The motherboard is disposed on the bottom board. The hard disk cage is fixedly connected to the fixing portions and above the tray, and has a hole corresponding to a hole of the front board. The hard disk drive may be disposed pluggably in the cage.