To provide an actuator unit exhibiting high degree of freedom in design through a simple structure and advantageous for miniaturization, in which there is no positional gap in the linkage posture of a nut plate and a movable object during and after action of impact, and the function as a driving force transmission system can be sustained while exhibiting impact resistance.

A stepping motor 29 is secured to a box-like support 1, and a nut plate 4 is meshed to a lead screw 3 provided on its output shaft 20. A lens frame 30 is disposed on the through hole 13 side, the nut plate 4 is mounted on a linkage 32 stretching from the substantially tubular body of the lens frame 30, an upper sprig member 6 and a lower spring member 7 are arranged vertically and then applied with a pressing force, thus linking the nut plate 4 integrally with the linking portion 32. The nut plate 4 is provided with a protrusion 5 extending in the feeding direction, and the protrusion 5 is fitted movably to a posture holding hole 36 provided in the linkage 32.