To provide a convenient radiation image generation system which is driven as a cassette being set in a cassette fixing body and being removed from the cassette fixing body, which is independent of a controller, and with which an image is taken even at a remote location.

The radiation image generation system includes a portable cassette type radiation image reading device which includes an X-ray source, an imaging panel for performing the reading of a radiation image according to radiation intensity from the X-ray source, a radiation detection means for detecting irradiation with radiation, a control means which controls the start of the reading by the imaging panel based on the detection, and a power supply means for supplying power to these, and the controller which obtains image data from the portable cassette type radiation image reading device. The control means of the portable cassette type radiation image reading device is configured to be able to control the start of the reading based on an X-ray exposure signal from the X-ray source or the controller, and the detection result of the radiation detection means.