The J-PARC LINAC accelerated the H-minus beam up to the energy of 181 MeV, which is the design value, on January 24th, and got the official license for the beam operation on February 27th, 2007. The beam losses are enough small that the detectable radiation leaks to the working area can be scarcely observed, while the inevitable activation of the beam-line components start slowly. In this paper, we briefly report the method used in the radiation shielding calculation of the J-PARC LINAC.