To provide a thin film magnetic head and its manufacturing method, capable of effectively preventing the protrusion of a coil conductor in an ABS direction caused by heat, and the disconnection of the coil conductor itself.

This thin film magnetic head is provided with at least an inductive writing head element including an upper core layer magnetically coupled to an upper magnetic pole for its front end, a lower core layer magnetically coupled to a lower magnetic pole for its front end, a coil conductor inserted between the upper and lower core layers, and a coil insolating layer formed by sandwiching the coil conductor. A heat diffusing member having a high heat conductivity characteristic is formed at least on a part of the coil insulating layer in the outside area of the upper core layer, or formed in the outside area of the upper core layer in contact with a part of the coil conductor or in a manner for constituting a part of the coil conductor.