In order to eliminate noise from an X-ray image by obtaining transform coefficients of a wavelet transform based upon information contained in tile-by-tile image data and obtaining image data based upon these transform coefficients, the entirety of a pre-processed original image is segmented into a plurality of tiles (S301). Wavelet transform coefficients of each tile obtained by segmentation are output (S302). Each tile is subjected to texture analysis and the results of analysis are output (S303). Next, a coefficient conversion is applied to the wavelet transform coefficients of each tile based upon the results of analysis (S304). High-frequency components among the transform coefficients are subjected to coefficient conversion. Next, an inverse discrete wavelet transform is applied to the wavelet transform coefficients of each area that has undergone conversion, whereby an image from which noise has been eliminated is output (S306).