1. An image processing apparatus for suppressing a pseudo color and color noise of an image sensed by using a single board color image sensor, comprising: a resolution reduction unit configured to generate, from a first image sensed by using the image sensor, a second image having a resolution and a frequency band lower than those of the first image; a suppressing unit configured to suppress a pseudo color and color noise of each of the first and second images; a resolution increase unit configured to restore the resolution of the second image processed by said suppressing unit; a calculating unit configured to calculate a ratio coefficient for performing weighted combination on a pixel of the first image processed by said suppressing unit, and on a pixel, which corresponds to the former pixel, of the second image having the restored resolution; and a combining unit configured to perform weighted combination on a color signal of the pixel of the first image processed by said suppressing unit, and on a color signal of the pixel, which corresponds to the former pixel, of the second image having the restored resolution, in accordance with the ratio coefficient, wherein if it is determined that a pixel of interest of the first image belongs to a region where a pseudo color is generated, said calculating unit calculates a first ratio coefficient based on a luminance of the pixel of interest belonging the first image, and a second ratio coefficient based on a color of the pixel of interest belonging the first image, and selects one of the first coefficient and the second coefficient, which further increases a weight of the pixel of the second image having the restored resolution, as the ratio coefficient for use in the combination.