To provide a switching transformer suitable for mass production capable of cost reduction, miniaturization by reducing a material cost and improvement in assembly properties while improving performance.

A coil bobbin having a conventional hoisting drum is not used, and a terminal is planted on a lower surface and a substantially reverse-T shaped core 3 equipped with middle leg is integrally provided on a terminal bench 1 with a substantially flattened upper surface. A coil 6 is wound by winding an electric wire 6a on a periphery of the middle leg core 3b protruded from the upper surface 1a of the terminal bench 1. A C-type core 4 is assembled into the resulting assembly.