In relation to the magnetic head using a polycrystalline Mn-Zn ferrite as a core material, a magnetic head manufacturing method is provided for preventing the generation of the post-recording noise which is a pulse noise generated immediately after the completion of a current flow through the recording and reproducing coil. A fused core block is manufactured using Mn-Zn ferrite having a mean crystal grain size of equal to or less than 30 .mu.m as the core material of at least the recording and reproducing head and glass fusion using one type of glass, and the fused core block is annealed at a temperature equal to or higher than the strain point of the glass.