An optical unit is disclosed which is capable of being easily assembled, enabling its optical element to smoothly move, and preventing friction loss from being generated around its nut member. A lens driving apparatus is provided for moving an optical element holder, which supports an optical element having an optical axis and is movable along a guide member, in an extension direction of the optical axis, using a nut integrally provided at the holder, and a lead screw threadedly coupled to the nut to rotate forward and backward by a driving unit. In the lens driving apparatus, the forward or backward rotation of the motor is transmitted to the lead screw via a reduction gear train. The lead screw is installed to be inclinedly movable with respect to the extension direction of the optical axis about threaded coupling portions of a threaded section of the lead screw and the nut.