An image processing apparatus includes a processing unit to perform noise reduction processing on image data and an output unit to output noise-reduced output image data. The processing unit determines a weight for a reference pixel based on a target area including a target pixel and a reference area including the reference pixel and sets, as a pixel value of the target pixel on which processed noise reduction processing has been executed, a value calculated using reference pixels and a weight corresponding to each of the reference pixels. The size of the target area equals to the size of the reference area. The output unit outputs, as the pixel value of the target pixel after noise reduction processing, either a first value, calculated when a first pixel group is set as the target area, or a second value, calculated when a second pixel group is set as the target area.