of the display device 36 as 34 1 line data 34 at this time 34 1 line data 34 is memorized in the memory being appropriate to a vertical line of the left side of a screen not shown of the display device 36 the next eight millisecond period 34 1 line data 34 is detected in the same way as described above the next 34 1 line data 34 is memorized in the direction to the right side of the previous 34 1 line data 34 in the memory and so forth so whenever the conveyor belt 25 moves two millimeters the 34 1 line data 34 is measured if the conveyor belt 25 moves one meter five hundred sets of 34 1 line data 34 are measured accordingly a scattered x ray beam image which is suitable for the article 26 is memorized in the memory of the display device 36 and is displayed on the screen of the display device 36 as described above according to this embodiment as the efficiency of measuring the scattered x ray beam and the primary x ray beam is improved the quality of pictures of the scattered x ray beam image and the primary x ray beam image are improved table 1 compares merit valves about the scattered x ray beam image and the primary x ray beam image of this embodiment and the prior.