A noise of an image signal generated by mixing a plurality of image signals is accurately estimated. In an image processing apparatus including an input unit and an estimation unit, a mixed image signal is input to the input unit, the mixed image signal being obtained by mixing a plurality of image signals with different exposure times that have been generated by an image sensor, on a basis of a predetermined mix ratio. The estimation unit is configured to estimate a mixed image signal noise being a noise of the mixed image signal, on a basis of the mix ratio, a noise characteristic coefficient indicating a noise characteristic of the image sensor, and a ratio between the exposure times in the plurality of image signals.