To provide an image pickup device and a lens system which can be miniaturized and can advantageously be made inexpensive.

A front lens 22 has a lens part 2202 and an attachment part 2203. An opening part 208 is formed in the size corresponding to the lens part 2202 and an abutted part 210 to which a first surface 2206 is abutted is formed on a wall part 206 around the opening part 208. An energizing member 2401 is composed of a spring material 2402 of a single thin plate shape. A spring piece 2406 is formed on a spring material 2402 part around an opening part 2404, is abutted to a second surface 2208 via a lens frame 2204 and, thereby, is constituted so as to energize the first surface 2206 in the direction of being abutted to the abutted part 210.