A composition unit generates a composite image by compositing a frame image of interest and a processed image obtained by applying minimum value filtering processing to the frame image of interest. An LPF processor generates a low frequency component image by applying low-pass filtering processing to the composite image. A difference detector generates a difference image between the frame image of interest and the low frequency component image, and an adder generates a high frequency component image by adding the difference image to the frame image of interest. The composition unit executes composition processing using a minimum composite ratio a so that all pixel values which configure a region in the high frequency component image corresponding to a steep edge region in the composite image are equal to or larger than zero.