Abstract: A radiation cassette comprises a casing which accommodates an accumulative fluorescent material sheet, a lid which is installed to a part of the casing so that the lid is openable and closable, a shield plate which is arranged for the casing and which is swingably provided with the lid at a first end, a support means which swingably supports the shield plate with respect to the casing, and a lock means which fixes the shield plate to the casing and which moves back and forth in accordance with an external force so that the shield plate may be released from fixation. Accordingly, it is possible to attach and detach the shield plate arranged for the casing by means of a simple operation.