A mixture ratio determiner chooses a first mixture ratio set in a case where a blur evaluation value is a reference value or more, and chooses a second mixture ratio set in a case where the blur evaluation value is less than the reference value. The second mixture ratio set has a higher mixture ratio of an in-focus image and a lower mixture ratio of an out-of-focus image than the first mixture ratio set. A mixed image generator produces a plurality of mixed images having a gradually varying mixture ratio, from the in-focus image and the out-of-focus image. A display controller sequentially displays the plurality of mixed images on a monitor in the manner of a moving image.