An image pickup apparatus detachably mounting a lens unit including a plurality of optical members includes an image pickup unit that accumulates charge in synchronization with a vertical synchronizing signal to generate an image signal, and a control unit that generates control information for each of the plurality of optical members of the mounted lens unit and communicates the control information with the lens unit in synchronization with the vertical synchronizing signal. The control unit is configured to perform a first communication in synchronization with the vertical synchronizing signal, and to perform a second communication, for controlling an optical member different to the optical before a next first communication that is performed in synchronization with a next vertical synchronizing signal. The first communication and the second communication are predetermined packet communications in which optical members to be controlled among the plurality of optical members are different from each other.