An image processing device includes a first wide dynamic range (WDR) image generation block, a control signal generator, and a second WDR image generation block. The first WDR image generation block processes a long-exposure image signal to generate a first image signal, processes a short-exposure image signal using a second weight value to generates a second image signal, and to synthesize the first image signal and the second image signal to generate a first WDR image signal. The control signal generator calculates a difference between the second weight value and a reference weight value and generates control signals according to a result of the calculation. The second WDR image generation block adjusts a noise level of the first WDR image signal using the control signals and generates a second WDR image signal according to a result of the adjustment.