Communication costs have become a performance bottleneck in many applications, and are a big issue for high performance computing on massively parallel machines. This paper proposes a halo exchange method for unstructured sparse matrix vector products within the algebraic multigrid method, and evaluate it on a supercomputer with mesh/torus networks. In our numerical tests with a Poisson problem, the proposed method accelerates the linear solver more than 14 times with 23040 cores.