PURPOSE: To constantly conduct the optimum outline accentuation, regardless of the kind of an endoscope adopted for the diagnosis site to observe, by controlling the image outline accentuation level to be the optimum value depending on a diagnosis site of a subject and on a kind of an endoscope to use.

CONSTITUTION: The endoscope-type-recognition signal from a endoscope-type- recognition-signal generator 5 in an endoscope is input in a optimum image- outline accentuation signal generator 22, and at the generator 22 the optimum image-outline accentuation signal by kind of endoscope, is generated to input in adders 11, 12, and 13. Then, the generated optimum image-outline accentuation signals are added to output signals of respective signal memories of 8, 9, 10 for R, G, and B at the adders 11, 12, and 13, and are turned into analogue image signals with the outline accentuated at the optimum value by D/A converters 14, 15, and 16. Thereby outline accentuation suited for an endoscope chosen depending on the diagnosis site can be carried out.