A magnetic assembly includes plural first magnetic cores, plural coil windings and a second magnetic core. Each of the plural first magnetic cores includes plural legs and a first connection part. The first connection part is connected with first terminals of the plural legs. The first connection part of the first magnetic core at an upper position is located adjacent to second terminals of the plural legs of the adjacent first magnetic core at a lower position. Each coil winding is wound around at least one leg of the plural legs of the corresponding first magnetic core so as to form a magnetic element of the corresponding converter. The second magnetic core is stacked over the plural first magnetic cores. The second magnetic core is located adjacent to the second terminals of the legs of the topmost first magnetic core.