Disclosed is a device for noise reduction using dual conversion gain, which includes an image sensor including a pixel array, the pixel array configured to generate a first pixel signal corresponding to a first conversion gain and a second pixel signal corresponding to a second conversion gain from pixels sharing a floating diffusion region and the image sensor configured to generate first image data and second image data based on the first pixel signal and the second pixel signal, and an image signal processor that generates an output image based on the first image data and the second image data. The image signal processor includes a normalization circuit that normalizes the first image data based on a dynamic range of the second image data to generate third image data, and a blending circuit that generates the output image based on the second image data and the third image data.