A bunk bed in an apartment consists of a bed, a bookcase, a wardrobe, a desk, and a ladder frame. The bookcase and wardrobe are connected to the inner side of the bed frame's legs. The desk connects the bookcase and the wardrobe together. A ladder frame is installed at one end of the bed frame where the bookcase is located, and there is a guardrail at the other end of the bed frame on the same side as the ladder frame. Under the desktop of the desk, there is a keyboard stand and a drawer frame. Since the bed is a three-dimensional space combination, it not only saves space but also is neat and beautiful, and easy to manage.