PURPOSE: To suppress vibration sounds of a bobbin associated with vibration of a gradient magnetic field coil.

CONSTITUTION: Technola (registered mark made by Teijin), an example of aromatic polyamide (aramid) fiber 5, is formed in a screen. A number of the fibers are wound on a cylinder mold and hardened with an epoxy resin or the like to form a bobbin 6 for a gradient magnetic field coil. As compared with the glass fiber reinforced resin as the conventional bobbin material, the amplitude at the resonance frequency of the aramid fiber reinforced resin is reduced to about one-fifth and the vibration attenuation time is higher. Thus, the vibration of the bobbin 6 associated with the vibration of a gradient magnetic field coil 10 can be suppressed more than the conventional product thereby reducing beating sounds reverberating inside the bobbin 6.