1. A visible and infrared light photographing lens system which enables the same object to be photographed simultaneously using a visible light and an infrared light, the system comprising: a focus lens which can be moved in a direction of an optical axis in order to focus on the object at a desired object distance; a light dividing device which divides an object light having passed through said focus lens, into an object light for a visible light and an object light for an infrared light and which guides the object light for the visible light and the object light for the infrared light through a visible light optical path and an infrared light optical path, respectively; a visible light image pickup device which picks up an object image of a visible light using the object light for the visible light; an infrared light image pickup device which picks up an object image of an infrared light using the object light for the infrared light; a compensation lens placed in at least one of the visible light optical path and the infrared light optical path so as to be movable in the direction of the optical axis, the compensation lens adjusting a position at which the object light passing through the compensation lens is formed into an image; and a compensation lens control device which controls a position of the compensation lens on the basis of a position of said focus lens so that an object distance to the object at which said visible light image pickup device can be focused on the object is equal to an object distance to the object at which said infrared light image pickup device can be focused on the object.