1. An image capturing apparatus comprising: an image sensor including a plurality of pixels arranged two-dimensionally; a shutter that shields said image sensor from light; a controller that controls to perform continuous shooting of a plurality of exposure images by said image sensor and compose the plurality of exposure images obtained by the continuous shooting; the controller that controls to acquire a first black image before the continuous shooting by causing said image sensor to accumulate electric charges while said image sensor is shielded from light by said shutter and to acquire a second black image after the continuous shooting by causing said image sensor to accumulate electric charges while said image sensor is shielded from light by said shutter; and an image processing circuit that performs first noise reduction processing using the first black image for each of a plurality of exposure images obtained by the continuous shooting and performs second noise reduction processing using the second black image for an exposure image obtained by composing the plurality of exposure images by said controller.