We examined the tunneling current behaviors of magnetic tunneling junction (MTJ) cells utilizing conductive atomic force microscopy (AFM) interfaced with an external magnetic field generator. By introducing current through coils, a magnetic field was generated and then controlled by a current feedback circuit. This enabled the characterization of the tunneling current under various magnetic fields. The current-voltage (I-V) property was measured using a contact mode AFM with a metal coated conducting cantilever at a specific magnetic field intensity. The obtained magnetoresistance (MR) ratios of the MTJ cells were about 21% with no variation seen from the different sized MTJ cells; the value of resistance $ imes$ area (RA) were 8.5 K-12.5 K $({Omega}{mu}m^2)$. Since scanning probe microscopy (SPM) performs an I-V behavior analysis of ultra small size without an extra electrode, we believe that this novel characterization method utilizing an SPM will give a great benefit in characterizing MTJ cells. This novel method gives us the possibility to measure the electrical properties of ultra small MTJ cells, namely below $0.1;{mu}m;{ imes};0.1;{mu}m$.