An image acquisition device including: an imaging optical system forming two images having parallax； and an element acquiring the parallax images, the imaging optical system includes: a first negative lens group having negative refractive power； a first positive lens group having positive refractive power； and a second positive lens group having positive refractive power, the first negative lens group includes two negative lens groups disposed side by side in the parallax direction and having central axes respectively, the first positive lens group is a common lens group having a single central axis, and light rays emitted from the negative lens groups pass therethrough, the second positive lens group includes two positive lens groups disposed side by side in the parallax direction and having central axes respectively and the first positive lens group includes a moving lens group moved along the central axis of the first positive lens group.
