The resolution of a magnetic force microscope with metal‐capped nanotube probes has been investigated from the theoretical and experimental points of view. The width of the line image of the magnetic information was measured as a function of the tip‐sample separation using a nanotube probe with a particle of Fe3C with a diameter of 50 nm. The theoretical calculation, which well explains this experimental result, indicates that the metal‐capped nanotube probes have a high potential for the high resolution imaging of the magnetic information. The resolution less than 10 nm is obtained when the nanotube tip with a diameter of ∼ 10 nm is scanned with the tip‐sample separation of ∼ 10 nm. © 2003 American Institute of Physics