To realize an image processing unit that can automatically obtain an image optimum to a diagnosis without the need for a troublesome operation by selecting an optimum filter for each area of a radioactive ray image.

The image processing unit that processes a radioactive ray picture obtained by detecting a radioactive dose transmitted through an object is provided with a filter storage means 50 that stores a plurality of filters the shapes and the sizes of masks of which are different, a filter selection means 40 that selects one or a plurality of filters among filters stored in the filter storage means, an image processing means 60 that conducts filtering processing on the basis of the filter selected by the filter selection means.