The invention relates to a rear converter lens apparatus to obtain a lens system having a focal length longer than that of a master lens device by the mounting of the master lens device, and a taking system comprising the same. A converter lens portion consists of, in order from an object side that is the master lens device side, a first lens group of positive refracting power, a second lens group of positive refracting power and a third lens group of negative refracting power. Between the respective lens groups there is a spacing. The first and second lens groups are located such that of axial air spaces in the converter lens portion, an air space between the first lens group and the second lens group is largest. One each lens group comprises a positive lens element and a negative lens element.