PURPOSE: To eliminate the noise component of a background picture before emphasizing a contour, and to emphasize a contour part more strongly than other part by executing a contour emphasizing processing by a differential filtering to a variable density picture which eliminated the noise component of the background picture.

CONSTITUTION: The output signal of an X-ray fluoroscopic device 10 is converted to the signal of a quantized and dispersed variable density picture by an A/D converter 14. The variable density picture is supplied to a picture contour emphasizing device 20, and stored successively at every corresponding picture element in its picture memory 21. In the picture contour emphasizing device 20, the variable density picture stored in the picture memory 21 is read out at every picture element by a picture element value converting part 22. A picture element having a picture element value being less than a prescribed gradation value is cleared and the noise component of a background picture is eliminated, to make a local variation emphasizing part 23 execute a differential filtering processing to this variable density picture, and to emphasize a local varied part. A display device 31 displays a binary-coded picture emphasizing the local varied part.