An imaging apparatus includes a lens unit to be mounted in one-touch on a module unit affixed by reflow soldering or the like to a base plate. When the lens unit is mounted in one-touch on the module unit, the conical outer circumferential surface of a tip-end part of a lens press-fitting part is in close contact with the inner circumferential surface of the conical concave part of the holder to regulate the coaxiality of the installed lens. A flange face of the lens is directly received and supported by the holder to regulate the parallelity with the imaging element and, in addition, when the lens unit is mounted in one-touch on the module unit, the barrel which is integrally formed with the lens press-fitting part is snap-locked onto the upper end part of the holder to ensure the fixing of the barrel.