Provided are a zoom lens device and a method for controlling the device, capable of reducing astigmatism regardless of the position of the zoom lens. In accordance with a zoom command, a lens constituting a zoom optical system is moved in the direction of the optical axis (step 81). The position of the moved lens is detected (step 82), and an amount of rotation corresponding to the detected position of the moved lens is read from a table that is stored (step 83). The lens is rotated by the read amount of rotation (step 84). As a result of the rotation of the lens, astigmatism in the zoom optical system is reduced.