An imaging lens (LN) of an imaging device (ID) is composed of an aperture stop (ST) and a lens unit (LU) having positive power. Even when the object side surface of the lens unit (LU) has a shape convexed to the side of the object, and a lens whose image side surface is concaved to the image side is used, excellent aberration performance with a short optical total length, a small sensor incidence angle and a small distortion are achieved at low cost.