In an electronic endoscope of the present invention, an edge detection circuit detects a down edge section and an up edge section of both ends of a blood vessel in a width direction based on a G signal output from an RGB color conversion circuit, an R coefficient selector and a B coefficient selector select, for example, a coefficient smaller than 1 for the detected down edge section and select, for example, a coefficient larger than 1 for the up edge section, and a multiplier multiplies an R signal and a B signal by these coefficients. As a result, both ends of the blood vessel are highlighted with a left end part expressed blackish and a right end part expressed reddish, making it possible to clearly display blood vessels in mucous membranes on a monitor. It is also possible to detect phases on a coordinate system where an R-Y signal is set on a vertical axis and a B-Y signal is set on a horizontal axis, compare these phases with reference phase ₁ of blood vessel colors and extract signals of blood vessel colors.