An image processing apparatus includes a first extraction section extracting first feature quantities from image data of an image of a subject captured in a first period; a first estimation section estimating a first average value of the first feature quantities on the basis of second feature quantities extracted from image data of an image of a registered subject captured in a second period and third feature quantities extracted from image data of an image of the registered subject captured in a third period; a second estimation section estimating a first distribution width indicating the width of dispersion of the first feature quantities with respect to the first average value on the basis of the second and third feature quantities; and a determination section determining whether or not the first feature quantities are within a predetermined range based on the first average value and the first distribution width.