A simple and practical image restoring device capable of improving the performance of image restoration. An image restoring device (100) is provided with a first restoration processing unit (160a) and estimates original image information from the degraded image information into which information unnecessary for the original image information is incorporated. A correlation calculating section (164) calculates the correlation value of the estimation error of when the state amount of a system at time n+1 including the original image information is estimated by information up to time n or the time n+1 with respect to the degraded image information of only the time n. A weighting factor calculating section (166) calculates a weighting factor to define the relationship of the optimum estimated value of the state amount at the time n+1 by the information up to the time n+1, the optimum estimated value of the state amount at the time n+1 by the information up to the time n, and an estimation error of an observed amount including the degraded image information by using the correlation value with respect to the degraded image information of only the time n. An optimum estimated value calculating section (168) calculates the optimum estimated value of the state amount at the time n+1 by the information up to the time n+1 by using the weighting factor with respect to the degraded image information of only the time n.