A lens apparatus comprises a barrel 100 which houses an imaging optical system including magnification-varying lens units 26 and 27, a focus lens unit 25, and a beam separation element 29 which separates a part of a light beam from an object out of a light beam directed to an imaging surface, operating members 1, 2, and 3 disposed on an outer circumference of the barrel and configured to be manually operated, a drive unit 200 disposed outside the barrel and including actuators 45 and 50 which drives each of the magnification-varying lens unit and the focus lens unit, and a controller 60 which controls the actuator, and a focus detector 31 disposed outside the barrel and configured to detect a focus state of the imaging optical system using the light beam separated by the beam separation element. The focus detector is embedded in the drive unit.