A magnetic element includes a bobbin assembly, at least one pancake winding assembly, a winding coil assembly and a magnetic core assembly. The bobbin assembly includes plural bobbin units. The plural bobbin units are detachably coupled with each other. Each bobbin unit includes a main body, a coupling structure and at least one engaging structure. The main body includes an external surface, a channel and a first winding section. The coupling structure is disposed on the external surface of the main body. The engaging structure of the bobbin unit is engaged with the engaging structure of an adjacent bobbin unit. The pancake winding assembly is disposed around the main body and coupled with the corresponding coupling structure. The winding coil assembly is wound around the first winding section. The magnetic core assembly is partially accommodated within the channel of the bobbin unit.