An image signal processing apparatus includes a sensing section which includes R, G, and B pixels and produces R, G, and B color signals, a first adding section which adds, while weighting pixels, a color signal of a center pixel of a pixel arrangement and color signals of the peripheral pixels to produce a first addition signal, a contour signal generating section which generates a contour signal from the color signals before the addition, a second adding section which adds the contour signal to the first addition signal to produce a second addition signal, a ratio coefficient calculation section which calculates a ratio coefficient of an average value of the R, G, and B color signals to a sum-up value of the average values, and an RGB signal generating section which generates new R, G, and B signals using the ratio coefficients and the first or second addition signal.