1. A noise-removing system comprising: an iris controller configured to control a degree of openness of a lens iris; a noise image analyzer configured to perform an analysis of a noise image that is obtained in a state when the iris controller closes the iris and obtain a mean and a standard deviation of the noise image based on the analysis of the noise image; a normal image analyzer configured to perform an analysis of a normal image that is obtained in a state when the iris controller opens the iris and obtain a mean and a standard deviation of the normal image based on the analysis of the normal image; and a noise remover configured to calculate a mean difference that is a difference between the mean of the noise image and the mean of the normal image, calculate a standard deviation difference that is a difference between the standard deviation of the noise image and the standard deviation of the normal image, calculate a weighted sum based on the mean difference and the standard deviation difference generate a noise mask based on the weighted sum, and obtain an image, from which noise is removed, by multiplying the normal image by the noise mask.