We examined a method for evaluating the cooling effects of trees for urban spaces using airborne LiDAR data. Voxel-based LAD distribution was derived from the data, and the distribution was applied to radiative transfer simulation to quantify solar transmittance and APAR. Subsequently, direct solar transmittance and transpiration rate of trees were calculated for an actual urban district, and several evaluations of these effects were performed. It was shown that the present method was able to quantify the cooling effects of trees while considering their structure, layout, and spatial geometry of the surrounding buildings.