[en] In order to measure the spatial distribution of neutrons in an accelerator room, the combined use of activation detectors and an imaging plate was tried. Activation detectors were set on monitoring points in the accelerator room. After the end of operation, the detectors were collected and pasted on the corresponding monitoring points on a lay-out plan of the accelerator room. The plan was overlaid with an imaging plate to develop the activity of activation detectors. This method is suitable for the simultaneous measurement of the activities of many detectors without any decay correction. The obtained image data are very useful for grasping the propagation of neutrons from the beam-loss points and to make an effective design for reducing the activation of the accelerator components and accelerator buildings. (author)