A cassette allows radiation image information stored therein to be used immediately after an X-ray radiation image is captured in a patient's room, and a mobile X-ray image capturing apparatus incorporates such a cassette. The mobile X-ray image capturing apparatus has a cradle serving as a mount for receiving the cassette which has a radiation detector. The mobile X-ray image capturing apparatus captures a radiation image of the patient (subject) in the patient's room. The cassette serves as a mobile station. While the cassette (mobile X-ray image capturing apparatus) is moving, the radiation image information stored in the cassette is transmitted to a server via a transmitting and receiving terminal, a mobile hospital communication network, and a hospital LAN.