A color signal processing apparatus for a multi-primary display with a simple circuit construction and a color signal processing method achieves a display white by more than four display primaries. The color signal processing apparatus has a tristimulus value calculation unit calculating tristimulus values (X, Y, Z) of an input color signal, a display primary control signal calculation unit calculating a control signal of each display primary to represent the color signal with a number of display primaries, and a control unit setting the control signal of each display primary with the control signal calculated by the display primary control signal calculation unit to display the color signal. Accordingly, the color signal processing apparatus for the multi-primary display is not only being capable of achieving the display white by more than the four display primaries but also can display the color signals of the entire color gamut according to the number of display primaries being provided and the settings for the respective color coordinates.