To provide an imaging apparatus with an autofocus function which is good in following ability and is stable and copes with a situation in which a subject changes largely.

In the imaging apparatus, an optical path separation part separates subject light converged by an optical system at least to a first luminous flux and a second luminous flux. An imaging part for photography converts the first luminous flux into an electrical signal and outputs it as a main line system video signal, an imaging part for autofocus converts the second luminous flux into an electrical signal and outputs it as a video signal for autofocus, and an autofocus evaluated value generation part generates a contrast evaluated value of a video. A control part achieves an AF function by automatically switching between a mode in which a focusing position is searched while changing optical path length of the second luminous flux on the basis of the contrast evaluated value, and a mode in which an optimum optical path length difference is calculated by situation and the focusing position is searched on the basis of size relation of the contrast evaluated values from a plurality of imaging parts for autofocus arranged with the calculated optical path length difference.