Abstract: The joined scintillator block body for radiation detector according to the present invention comprises a plurality of scintillator blocks, each being divided into small scintillator chips through deep grooves formed by cutting each block from the light-incident side and filled with a reflecting material and these plurality of blocks being joined together, wherein a part of the joined faces of each neighboring two blocks is joined with the reflecting material and the remaining portion thereof is joined with a transparent resin layer capable of transmitting scintillation light rays emitted by the scintillator chips. In the foregoing joined scintillator block body for radiation detector, all of the divisions or scintillator chips of the joined scintillator block body have the same ability of light emission and, therefore, the radiation can always be detected at any portion on the photomultiplier tube under the sam conditions.