To provide a driving lens unit for which a lens block and a driving unit are easily assembled, and a method for assembling the driving lens unit.

The driving lens unit is provided with a housing (11) fixed in the main body of a camera, a lens block (17) which his supported on the housing and linearly movable between a retracted position at which the lens block is accommodated in the deepest rear place in an optical axis direction and a projected position at which the lens block is extended to the mostly forwarded position, an engaging part (19) formed on the outer face of the lens block, a driving unit (22) which has a engaging member (24) linearly driven in the direction parallel with the optical axis and is attachable and detachable to/from the housing. The engaging member and the engaging part are engaged and disengaged with/from each other in the direction perpendicular to the direction of motion of the engaging member when the driving unit is attached to and detached from the housing, and the engaging member and the engaging part are moved together at the engaged state.