To provide a coil bobbin, in which an increased number of pin terminals are provided while the size is the same as conventional one, and a transformer, for which automatic winding can be done, causing no bridging of solder and which has the same characteristics and size as conventional devices.

A wire is wound on a coil bobbin consisting of a cylindical core made of an insulating material, an upper collar and a lower collar formed on both sides of the core, a plurality of projecting sections 2 where pin terminals 3 are planted and which are formed on both opposed side faces of the lower collar and pin terminals 3 so planted as to form triangles whose vertexes are the ends of the sections 2, and a magnetic core is assembled.