1. An image processing apparatus comprising: an imaging unit for outputting an imaging result as a time-series image; and an image correction unit, to which the time-series image outputted from the imaging unit is inputted as an input image, for correcting image fluctuation in the input image, wherein the image correction unit includes: a temporally-smoothed image generation section which generates, based on a plurality of time-series input images from the imaging unit, a temporally-smoothed image by smoothing the plurality of the time-series input images; a similarity determination section which sets a local area for the temporally-smoothed image generated by the temporally-smoothed image generation section and determines similarities between the local area in the temporally-smoothed image and partial areas of the plurality of the time-series input images; and a corrected image generation section which selects, from the partial areas of the plurality of the time-series input images, a partial area of one of the plurality of the time-series input images having an image most similar to an image of the local area of the temporally-smoothed image based on a similarity determination result calculated by the similarity determination section, and generates a corrected image based on the selected partial area.