A lens unit structure for an SLR digital camera is provided with a photographing lens block and a finder block. The photographing lens block includes a lens barrel having a pair of guide shafts extending in parallel with an optical axis. Ends of the guide shafts are secured to the lens barrel. A focusing lens and a zoom lens are slidably supported by the guide shaft so as to move in a direction of the optical axis, but prevents the lenses from moving in a direction perpendicular to the optical axis. The finder block includes a casing that accommodates a finder optical system, a CCD, and a beam splitter. The beam splitter splits the light from the photographing lens block into components directed to the finder optical system and the image capturing element. The casing has a plurality of holes respectively receiving the pair of guide shaft members.