An image processing device includes a signal processing circuit, a chromatic aberration extraction circuit, and a diaphragm control circuit. The signal processing circuit generates image data by signal-processing output data generated by an image sensor in accordance with light passing through a diaphragm and a lens. The chromatic aberration extraction circuit extracts a chromatic aberration from the image data. The diaphragm control circuit changes an f-number of the diaphragm. The diaphragm control circuit sets the f-number of the diaphragm based on the chromatic aberration extracted by the chromatic aberration extraction circuit.