PURPOSE: To obtain a laminated core proper to the miniaturization and flattening of a transformer by bringing the shapes of magnetic plates to at least two kinds or more of different forms and forming sections shaping the outer side surfaces of each magnetic plate to the same shape.

CONSTITUTION: A bobbin 11 on which a coil 12 is wound takes approximately a trapezoid, and an internal core 13a in a laminated core 13 inserted into the bobbin 11 also takes approximately the trapezoid. On the other hand, the upper surface of a side section core 13b is positioned at a section upper than the upper surface of the internal core 13a in the side section core 13b, and the side section core 13b takes a sectional shape forming a right angled triangle in which the upper surface and the side surface approximately cross at a right angle. The internal cores 13a in a pair of the laminated cores 13, 13 are inserted into the hole section of the bobbin 11 on which the coil 12 is wound previously from both sides of the bobbin 11, and each end surface of the internal cores 13a and the side section cores 13b is joined and bonded and fixed. A magnetic path is shaped by the internal cores 13a and side section cores 13b in a pair of laminated cores 13, 13. The outer side surfaces of the laminated cores 13, 13 are formed to a plane.