1. An image processing apparatus comprising: an image sensor that has an RGBW array including R, G and B pixels which are light receiving elements corresponding to wavelength lights of each RGB color and a W pixel which is a light receiving element receiving substantially all RGB wavelength light; and an image processing unit that performs image processing by inputting a sensor image formed of an RGBW pixel signal output from the image sensor, wherein the image sensor has a periodic array of a unit composition formed of each RGBW pixel, and has an array in which composition ratios of the R, G and B pixels within the unit composition are the same as each other and wherein each row and column of the periodic array are configured so that one W pixel is interposed between each of the R, G and B pixels and the R, G and B pixels are sequentially arranged in each row and column, and wherein the image processing unit converts a pixel array of the sensor image formed of the RGBW pixel signal, and performs at least either array conversion processing for generating an RGB array image or signal processing for generating each RGB image signal in which all RGB pixel values are set for each pixel position of the sensor image.