In recent years, there are case of applying CLT deck to road bridge decks. Most of general road bridge slabs are made of reinforced concrete. If CLT is applied to replace the existing RC slab, it can be expected to prevent the increase in dead load. However, consideration of mechanical characteristics of CLT slab with different support condition is not implement. The purpose of this study is to investigate the mechanical characteristics of CLT with different support condition, and consider the layer composition. As a result of this study, deflection is reduced when parallel layer is placed on outside, and difference of displacement and stress with support condition is small.