Provided are a lens device, an imaging device, a lens driving method, and a lens driving program capable of improving imaging quality by minimizing the positional displacement of a movable lens due tothe operation of an operation member. The lens device 11 includes: a focus lens 22 that can move along an optical axis; an operation signal acquisition unit 21a for acquiring an operation signal in accordance with the rotation amount of a movable operation member 31; a smoothing unit 21d for smoothing the operation signal; and a movable lens driving unit 21e for driving the focus lens 22 on the basis of the smoothed operation signal. The smoothing unit 21d controls the degree of smoothing on the basis of the ratio of the driving amount of the focus lens 22 based on the operation signal to thedepth range determined by the present position of the focus lens 22.