For Alloy 600 which is Ni based super alloy, the relation between sensitization and magnetic properties was studied from the view point of chromium depletion distribution. Experimental results of magnetic hysteresis (B-H) curves were compared with calculation results by Monte Carlo simulation including the information of the chromium depletion and both results showed good correspondence each other for their residual magnetizations and magnetic coercivities. Moreover, local magnetic hysteresis was measured by micro Kerr magnetometer for the area of inner grain and on grain boundaries. The result showed anisotropy on grain boundaries for the direction of magnetic field. The result is analyzed using a magnetic cluster formed as wire type which was derived from the chromium distribution estimated by energy dispersive X-ray spectroscopy of scanning electron microscope.