PURPOSE:To attain rapid reading by ringing an insulating film into contact with the surface of a semiconductor film forming an electrostatic charge distributed image corresponding to X-ray intensity distribution to transfer electrostatic charge, winding the insulating film around a drum, rotating the drum rapidly, and moving a charge detecting probe to convert the charge distribution into an electric signal. CONSTITUTION:The polyester film (insulating film) 2 on which an aluminum film 1 is deposited is wound around the conductive drum 3, and while being rotated together with the drum 3, positively charged by a corona electrifier 4. Then, the charged polyester film 2 is sticked to a 4-layer base consisting of an Al base 5, a fluorescent film 6, a transparent conductive film 7, and an amorphous silicone film 8. The distribution of charge on the polyester film 2 is detected by a charge detecting probe 11 while rotating the conductive drum rapidly and an electric signal from the probe 11 is inputted to an image processing and storing device 13 through an amplifier 12, and displayed on an image display device 14 if necessary. The probe 11 is moved in parallel with the shaft of the conductive drum 3 so as to cover the whole area of the film 2 and the time required for reading can be shortened in accordance with the number of probes.