An image pickup apparatus which is capable of optimizing the responsiveness of linear changes in focus to operations of a ring member without sacrificing the operability of the ring member, while using a small-sized, low-cost ring member for manual operations. The rotating operation state of a focus ring 600 is detected by ring rotation sensors 603, 604. A camera microcomputer 116 causes a focus lens 105 to be moved and stopped in an optical axis direction thereof based on results of the detection by the ring rotation sensors 603, 604. The camera microcomputer 116 controls the responsiveness of linear changes in focus to the rotating operation state of the ring member detected by the ring rotation sensors 603, 604 in accordance with at least the depth of focus.