PURPOSE: To inexpensively manufacture a pulse transformer with less irregularity of inductance by securing a magnetic permeable material interposed to regulate the inductance on the opposed surface of the first and second cores to any of two cores or coil bobbins.

CONSTITUTION: A core is composed by opposing the first core such as an E- shaped core 2 and the second core such as an I-shaped core 3, and coils 7, 8, 9 wound on a coil bottin 6 are mounted on the core 1. The material of the bottin 6 employs a magnetic permeable material. The bobbin 6 has a coolar 6a at one side, and the collar 6a is interposed as an inductance regulating magnetic permeable material in a gap (t) between the opposing surfaces of the cores 2 and 3. The coils 7W9 are wound on the outer periphery of the cylindrical portion 6b of the bobbin 6, and the core at the center of the core 2 is inserted into the portion 6b. Thus, the mean magnetic path length and the magnetic permeability can be equalized to suppress the irregular inductance of a transformer.