A transformer with a connector is described, having a primary side and a secondary side and composed of a winding base, a core and windings, wherein the core is inserted into the winding base and the windings are wound on the winding base, and the transformer is characterized in that a connector is disposed at the secondary side of the transformer and connected to an external connector disposed at a load to which a signal fed through the primary side to the transformer is outputted when the connector and the external connector are connected to each other. In the transformer, the connector conventionally disposed on the circuit board is disposed on the transformer, saving the space that would otherwise be needed for connection wires between the transformer and the connector. Therefore, the circuit board has a reduced area, effectively saving the manufacturing cost for a product to which the circuit board is applied.