In order to investigate the effect of ground solidification method for reducing the seismic damage of caisson type quay-wall, a series of shaking table tests in 1g gravitational field were performed in terms of the shear strength and the improvement width of ground solidification. The main conclusions obtained from this study are as follows: 1) Ground solidification behind caisson type quay-wall is effective for reducing the seismic damage of caisson type quay-wall and, however, setting backfill stones in solidified ground is not useful for the stability of quay-wall in current experimental condition for this study. 2) For solidified ground with large shear strength, the seismic behavior of quay-wall sympathizes with solidified ground as if both of solidified ground and quay-wall are a combined structure. Consequently, the seismic earth pressure from liquefied sandy ground is absorbed by solidified ground reducing the seismic earth pressure to quay-wall. 3) A formula to evaluate the sliding safety of caisson type quay-wall with solidified ground is proposed considering the cohesive component of shear strength of solidified ground. Based on the proposed formula, the improvement width for ground solidification method can be reduced from a conventional width in current design code.