Illuminance simulation was conducted to provide an efficient glass greenhouse structure considering daylight. As a result of the simulation, the triangular roof type of the glass greenhouse was better than the arch type roof with respect to the illuminance characteristic. When the height of the triangular roof was lowered, the illuminance characteristics and the uniformity of illumination were larger and greater. However, the location of the roof corners has little effect on lighting characteristics. In addition, it was confirmed that the optimum design condition when the installation orientation angle of the glass greenhouse was 90°. The higher the transmittance of the glass in the glass greenhouse, the better the illuminance and the uniformity ratio of illumination. Especially, the effect was greater when the glass transmittance was 60% or more.