A method for monitoring inside a chamber of a coke oven comprising: obtaining chamber width data and chamber wall image data in different extrusion cycles at a same location in a same carbonization chamber in a coke oven; calculating and numerically processing a finite difference between the chamber width data in a current extrusion cycle and the chamber width data in a past extrusion cycle and a finite difference between an area of a chamber wall damaged portion in the current extrusion cycle and an area of a chamber wall damaged portion in the past extrusion cycle using the chamber wall image data; obtaining a conical volume of a changed portion of the chamber wall from a distance X L along an X axis obtained from the calculated and numerically processed finite difference from the chamber width data and an area S of a peeled off portion obtained from the calculated and numerically processed finite difference from the chamber wall image data; and determining a chamber wall abnormality in accordance with a change in the volume and a change in the area, wherein the method further comprises: calculating and numerically processing the finite difference between the chamber width data in the current extrusion cycle and the chamber width data in the past extrusion cycle and the finite difference between the area of the chamber wall damaged portion in the chamber wall image data in the current extrusion cycle and the area of the chamber wall damaged portion in the chamber wall image data in the past extrusion cycle; and comparing the calculated and numerically processed finite difference from the chamber width data with a predetermined value for chamber width data, and comparing the calculated and numerically processed finite difference from the chamber wall image data with a predetermined value for chamber wall image data. obtaining chamber width data and chamber wall image data in different extrusion cycles at a same location in a same carbonization chamber in a coke oven; calculating and numerically processing a finite difference between the chamber width data in a current extrusion cycle and the chamber width data in a past extrusion cycle and a finite difference between an area of a chamber wall damaged portion in the current extrusion cycle and an area of a chamber wall damaged portion in the past extrusion cycle using the chamber wall image data; obtaining a conical volume of a changed portion of the chamber wall from a distance X L along an X axis obtained from the calculated and numerically processed finite difference from the chamber width data and an area S of a peeled off portion obtained from the calculated and numerically processed finite difference from the chamber wall image data; and determining a chamber wall abnormality in accordance with a change in the volume and a change in the area, wherein the method further comprises: calculating and numerically processing the finite difference between the chamber width data in the current extrusion cycle and the chamber width data in the past extrusion cycle and the finite difference between the area of the chamber wall damaged portion in the chamber wall image data in the current extrusion cycle and the area of the chamber wall damaged portion in the chamber wall image data in the past extrusion cycle; and comparing the calculated and numerically processed finite difference from the chamber width data with a predetermined value for chamber width data, and comparing the calculated and numerically processed finite difference from the chamber wall image data with a predetermined value for chamber wall image data. calculating and numerically processing the finite difference between the chamber width data in the current extrusion cycle and the chamber width data in the past extrusion cycle and the finite difference between the area of the chamber wall damaged portion in the chamber wall image data in the current extrusion cycle and the area of the chamber wall damaged portion in the chamber wall image data in the past extrusion cycle; and comparing the calculated and numerically processed finite difference from the chamber width data with a predetermined value for chamber width data, and comparing the calculated and numerically processed finite difference from the chamber wall image data with a predetermined value for chamber wall image data.