A correlated double sampling device (CDS device) of an image sensor is provided. The CDS device is coupled to a plurality of light-sensing pixels arranged along a first direction. The CDS device of the image sensor includes a regulator and a sampling circuit. The regulator provides the light-sensing pixels with a first voltage so that at least one of the light-sensing pixels provides a first linear current and a second linear current according to the first voltage. The sampling circuit is coupled between a second voltage and the regulator and includes a first sampling unit and a second sampling unit to respectively receive the first linear current for a first duration and the second linear current for a second duration and to respectively and correspondingly output a first sampling signal and a second sampling signal.