A replaceable panel device (1) includes a panel (20) with a mounting portion (24), a locking subassembly (30), and a top cover (40) with a block (45). The mounting portion has at least one slideway (241), a recess (242), and two locating grooves (243). The locking subassembly is accommodated in the mounting portion of the panel. The locking subassembly has a button (31), an elastic rod (32), and a slider (33). The button has at least one rail (312), a hole (313) defined at top of the rail. The slider has at least one slot (331) and a rabbet (332). The slider is received in the recess. The rail is received through the slideway and the slot. The elastic rod is received through the hole. Ends of the elastic rod are located in the locating grooves. The rabbet engagingly receives the block of the top cover.