An imaging system includes incidence faces composed of optical faces having an image focusing function; prisms; and exit faces. The incidence faces are arranged with a first pitch along a first axial direction. The prisms are arranged with a second pitch along the first axial direction. The exit faces are arranged with a third pitch along the first axial direction. The first axial direction is set as a Y direction. A normal line direction of a face top of an optical face of the incidence face in a plane perpendicular to the first axial direction is set as a X direction. A direction perpendicular to the Y direction and the X direction is set as a Z direction. In a XZ cross-section plane, a width of the prism in the Z direction is smaller than a width of optical face of the incidence face in the Z direction.