A lens module includes a first lens. The first lens includes a first central round portion and a first peripheral portion. The first peripheral portion has a first radially extending portion surrounding the first central round portion, and a first axially extending portion extending axially from the first radially extending portion. The first radially extending portion comprises a first surface. The first axially extending portion comprises a first cylindrical side surface and a second side surface. The first cylindrical side surface is interconnected between the second side surface and the first surface. The first cylindrical side surface is coaxially aligned with a principal axis of the first central round portion and the second side surface is inclined relative to the principal axis of the central round portion.