1. A moving image noise reduction processing apparatus for reducing noise in a digitalized time-series image signal, comprising: a spatial noise reduction unit applying spatial noise reduction processing to the image signal; an image signal storage unit storing an image signal to which at least the spatial noise reduction processing has been applied; and a temporal noise reduction unit performing temporal noise reduction processing based on an image signal to be processed to which the spatial noise reduction processing has been applied in the spatial noise reduction unit and an image signal which is stored in the image signal storage unit and is earlier than the image signal to be processed.