1. An image processing apparatus for reducing a blur in an input image, said image processing apparatus comprising: a noise processing unit including: a noise reduction unit configured to perform noise reduction processing to the input image in a spatial domain, to generate a noise-reduced image; a first fluctuation range setting unit configured to set a first fluctuation range, such that the first fluctuation range decreases with respect to an increase in frequency; and a frequency restriction unit configured to perform noise processing to modify the noise-reduced image to generate a noise-processed image such that a variation indicating a magnitude of a degree of variation does not exceed the first fluctuation range; and a restoration processing unit configured to perform image restoration processing that reduces a blur to the noise-processed image, the image restoration processing being performed according to a degree of restoration, wherein said noise processing unit is configured to perform the noise processing such that the degree of variation, according to which the noise processing is performed by said noise processing unit, becomes more restricted as the degree of restoration, according to which the image restoration processing is performed by said restoration processing unit, increases.