PURPOSE: To prevent deformation of a magnetic core and to fabricate a mag netic gap with high accuracy.

CONSTITUTION: A magnetic core 1 which is provided with a coil assembly 3 for electromagnetic conversion and forms a magnetic flux path for a magnetic gap 4 contacting and sliding to a magnetic recording medium has a projecting part (c) which forms flatly a surface of the magnetic core 1 forwarding to the magnetic gap 4 and is faced at the magnetic gap 4, and a step part (h) which is formed at a base section of the projecting part (c). And end parts of core holders 2a, 2b are contacted to the step part (h) and the magnetic gap 4 part is precisely fabricated, and the core holders 2a, 2b are attached in a shield case 5 having an exposed opening 5a which exposes the magnetic gap 4 part to the outside in the state in which core holders 2a, 2b are contacted to the step part (h).