A server includes a case and function modules. The case includes a frame, a first upright partition and a second upright partition. The frame has an internal space and an opening. The opening corresponds to the internal space. The first upright partition and the second upright partition jointly define a first accommodating portion, a second accommodating portion and a third accommodating portion in the internal space. Each of the function modules is a first function module, a second function module or a third function module. A width of the first function module is half of the width of the second accommodating portion. The width of the first function module, a width of the second function module and a width of the third function module have a ratio of 1:2:4.