To reduce unnecessary operation by increasing a driving speed when detecting a starting point for a lens.

The lens device has an automatic iris mode in which the relative position of an iris mechanism 50 is controlled, and an adjustment is made so that a quantity of incident light of an optical system is kept constant. The lens device includes: an iris motor 56 that drives an iris mechanism 50; an iris starting point detecting means 60 for detecting a reference position for the iris mechanism 50; a relative position detecting means 59 for detecting a relative position using the initial position of the iris mechanism 50 as a reference; and a CPU 70 that, after a power source is turned on, drives the iris mechanism 50, detects the reference position of the iris mechanism 50, and, after the initialization of the iris mechanism 50, returns the iris mechanism 60 to the position used before this initialization. The driving speeds of the iris motor 56 before and after the detection of the reference position are set to the highest one which the iris motor 56 can manage. The iris mechanism 50 is changed to the automatic iris mode in front of the position where the iris mechanism 50 is returned to the position used before the mechanism 50 is initialized after the detection of the reference position.