The utility model relates to a radiation detecting device for a container, which comprises a radiation source 1, a collimator 2, a detector array 3, a travelling crane 5, rolling linear guide rails 6, a bracket 7 of the radiation source and a shield room 4 of a building. The radiation source 1, the collimator 2 and the detector array 3 are all installed in the shield room 4 of a building. Common guide rails are changed into the rolling linear guide rails; the structure of the travelling crane and the technique that the detector array is installed on the lateral surface are adopted. The utility model has the advantage of simple structure. The definition of images is increased. The installation, the maintenance and the replacement of the detector array are facilitated. In addition, the inner part of the shield room 4 of a building is enabled to be cleaner.