An image synthesizing device comprising: an image capturing unit configured to capture a plurality of images that are temporally continuous and that are comprised of pixels having pixel values; wherein capture angles of the respective captured images are substantially same, a drive controller that controls the exposure amount of the captured images, a first difference obtaining unit configured to obtain differences of said pixel values between a first image and a second image of the plurality of images on pixel-by-pixel basis, a blending unit configured to employ the differences between the first image and the second image as transparency information, characterized in that the drive controller controls the exposure amount of the respective captured images to be different from each other to obtain an underexposed first image with a reduced exposure amount with respect to an appropriate exposure amount and to obtain an overexposed second image with an increased exposure amount with respect to the optimal exposure amount, wherein an exposure amount of the first image, which is underexposed, is smaller than that of the second image, which is overexposed, and by comprising a gain controller configured to increase a brightness gain for said pixel values of the first image of the plurality of images such that an exposure amount of the first image is equivalent to an exposure amount of the second overexposed image of the plurality of images, wherein the first difference obtaining unit is configured to obtain differences of said pixel values between the first image provided by the gain controller and the second image on pixel-by-pixel basis, wherein the blending unit configured to employ the differences between the first image provided by the gain controller and the second image as transparency information, and to blend the first image provided by the gain controller and the second image by using the transparency information to obtain a blended image, and an image generator configured to generate a single synthesized image by adding pixel values of the first image provided by the image capturing unit and the obtained blended image. an image capturing unit configured to capture a plurality of images that are temporally continuous and that are comprised of pixels having pixel values; wherein capture angles of the respective captured images are substantially same, a drive controller that controls the exposure amount of the captured images, a first difference obtaining unit configured to obtain differences of said pixel values between a first image and a second image of the plurality of images on pixel-by-pixel basis, a blending unit configured to employ the differences between the first image and the second image as transparency information, characterized in that the drive controller controls the exposure amount of the respective captured images to be different from each other to obtain an underexposed first image with a reduced exposure amount with respect to an appropriate exposure amount and to obtain an overexposed second image with an increased exposure amount with respect to the optimal exposure amount, wherein an exposure amount of the first image, which is underexposed, is smaller than that of the second image, which is overexposed, and by comprising a gain controller configured to increase a brightness gain for said pixel values of the first image of the plurality of images such that an exposure amount of the first image is equivalent to an exposure amount of the second overexposed image of the plurality of images, wherein the first difference obtaining unit is configured to obtain differences of said pixel values between the first image provided by the gain controller and the second image on pixel-by-pixel basis, wherein the blending unit configured to employ the differences between the first image provided by the gain controller and the second image as transparency information, and to blend the first image provided by the gain controller and the second image by using the transparency information to obtain a blended image, and an image generator configured to generate a single synthesized image by adding pixel values of the first image provided by the image capturing unit and the obtained blended image.