PURPOSE: To observe the distribution condition of the charge in a furnace continuously in real time by disposing electrode bars in different height and radial directions in the wall part of the furnace body, determining the data on changes in electric resistance and displaying the same in images.

CONSTITUTION: The plural electrode bars 3a1W3f4 are provided to the different positions in the height and radial directions in the wall part of the blast furnace body 1. The output signals of the respective electrode bars 3a1W3f4 are inputted to a signal selecting mechanism 4 which switches the electrode bars 3a1W3f4 in arbitrary order by the program of a microcomputer 5. The output signals of the signal selecting mechanism 4 are inputted to an electric resistance measuring mechanism 6 which in turn measures the electric resistance values between the respective electrode bars 3a1W3f4. The values are converted to digital processing signals 7a by an arithmetic processing mechanism 7 and are displayed on an image display part 8 via an image processing part 8a. The distinct condition of the change in the furnace is thereby continuously recognized.