  We calculate the combinatorial $R$ matrix for all elements of
$\mathcal{B}_l\otimes \mathcal{B}_1$ where $\mathcal{B}_l$ denotes the
$G_2^{(1)}$-perfect crystal of level $l$, and then study the soliton cellular
automaton constructed from it. The solitons of length $l$ are identified with
elements of the $A_1^{(1)}$-crystal $\tilde{\mathcal{B}}_{3l}$. The scattering
rule for our soliton cellular automaton is identified with the combinatorial
$R$ matrix for $A_1^{(1)}$-crystals.
