To produce a radiation detector easily, quickly, accurately and at a low cost.

An electrode plate 1 cut in a specified size in advance is inserted along the groove 4 in a jig frame 3, slide to the bottom and contacted to the lower support plate. This work is repeated for the number of the grooves 4. Another support plate in the upper side is put on the opening drilled in the jig frame 3 and contacted to the upper surface of each electrode plate 1 already inserted and then the jig frame 3 is drawn. In this manner, a large number of radiation detectors can be produced and the accuracy of the arrangement pitch of the electrode plates can be raised.