A detachable transformer includes a first bobbin, a primary winding, a second bobbin, a secondary winding and a magnetic core set. The magnetic core set peripherally surrounds the first bobbin and the second bobbin and is inserted into them. A top and a bottom of the first bobbin respectively have a first winding recess and an installation recess. The primary winding is arranged in the first winding recess. A side of the installation recess has a first opening connecting with an external space. A top of the second bobbin has a second winding recess. The secondary winding is arranged in the second winding recess. The second bobbin is arranged in the installation recess through the first opening, whereby the first bobbin and the second bobbin form a detachable connection.