According to an embodiment, a high dynamic range synthesizing circuit includes an interpolation processing unit, a blur detection unit and a mix processing unit. The interpolation processing unit generates an interpolation signal. The blur detection unit uses a first image signal and a second image signal a signal level of which is adjusted for detecting the amount of blur. The mix processing unit performs processing of mixing the second image signal into the interpolation signal. The mix processing unit applies a weight of the second image signal depending on the amount of blur to the interpolation signal by the mix processing.