In this study, we analyzed the environmental impact of medium-rise apartments built using cross-laminated timber (CLT) and compared it to that of reinforced concrete (RC) housing. I found that CLT housing generates lower greenhouse gases (GHGs) than RC housing. To achieve further reductions, it is important to reduce the generation of GHGs during manufacturing of raw-material materials due to the use of biomass fuels in the drying process during the production of CLT. Furthermore, it is essential to reduce energy consumption during exploitation. A total environmental impact assessment was conducted using LIME2; the results showed that the total value of CLT housing had a similar impact as RC housing. To further decrease the environmental impact, it is essential to reduce the manufacturing load and extend the service life of materials used in new construction, specifically CLTs, joint fittings, and gypsum boards, and reduce energy consumption during exploitation. In addition, reducing the impact of building waste disposal is also essential, particularly in reducing the amount of waste generated for landfill disposal.