The present disclosure is directed to a converter lens device that includes a first mount to which a master lens device is capable of being attached, a second mount to which a camera body is capable of being attached and a converter lens having a negative refractive power, wherein, an optical system comprising the converter lens device and the master lens device has a focal length longer than a focal length of an optical system of the master lens device, the converter lens comprises sequentially from an object side, a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, and a third lens unit.