A transformer with fixed pins is disclosed. The transformer includes a bobbin, a primary winding, a secondary winding, a core set and a plurality pins. The primary and secondary windings are wound around the bobbin and both have a plurality of winding ends. The core set surrounds the primary and secondary windings. Each of the pins is fixed upon the bobbin and electrically connected with a corresponding winding end. The transformer further includes a fixing plate, and the pins are fixed upon the bobbin through the fixing plate.