The present invention relates to a planar transformer, the transformer including a core provided to induce formation of a magnetic field, a bobbin coupled to a core, at least one primary winding interposed between the core and the bobbin to supply a power signal, a first insulation unit provided to the at least one primary winding to insulate the at least one primary winding, at least one secondary winding provided to the first insulation unit and insulated by the first insulation unit to transform the power signal, and a second insulation unit provided to the at least one secondary winding to insulate the at least one secondary winding.