An imaging device acquires a plurality of viewpoint image signals having different viewpoints from an imaging element. The imaging device selects a subject region within a captured image, and divides the subject region into a plurality of regions. The imaging device performs a correlation operation for each divided region, and calculates an amount of parallax on the basis of one or more extreme positions. In addition, the imaging device calculates distance information of a subject on the basis of the amount of parallax, and calculates a reliability for the distance information. If there are two or more pieces of distance information which are output in the divided region, the imaging device generates a distance histogram using the two or more pieces of distance information based on the reliability.