1. An image processing apparatus, comprising: a reduced image generation section generating, at least at one reduction ratio: (i) a first reduced image obtained by reducing a target image, which is a target of noise reduction processing, and (ii) a second reduced image obtained by reducing a reference image at a same reduction ratio as a reduction ratio of the first reduced image; a noise extraction section extracting a noise component in a frequency band corresponding to the reduction ratio of the first reduced image by using the first reduced image and the second reduced image; and a noise reduction section reducing the noise component in the frequency band from a pixel value of each pixel of the target image based on the noise component in the frequency band extracted by the noise extraction section; wherein when a plurality of pairs of the first reduced image and the second reduced image are generated at a plurality of reduction ratios, the noise extraction section sequentially extracts the noise component in the frequency band from a pair whose reduction ratio corresponds to a minimum reduction ratio.