Additive Manufacturing（AM）has great potential to produce end-use parts with greater complexity of geometry than traditional methods. Amidst various AM technologies, selective laser sintering（SLS）has quickly been commercialized for production of end-use parts. However, the applications are still limited due to material constraints. In our previous study, SLS process suitable for polybutylene terephthalate（PBT）using a commercial machine was performed by applying copolymer type PBT powder. This study investigated the influence of thermal aging during SLS process on PBT powder to establish the recycling technology for PBT powder. Recycling of PBT powder was conducted two times to clarify the aging effects, and the following results were obtained. Flowability of aged PBT powder dropped about 20％compared to virgin PBT powder. This main reason is considered to be a decrease in the amount of the humed-silica coating around the powder particles. Melt volume rate of PBT powder decreased by about 75％after recycling two times. This result indicates that molecular weight of PBT powder increased due to annealing effect during the SLS process. Shrinkage and warpage of SLS parts in the x-direction were reduced in case of using aged PBT powder. These phenomena are thought to be causedbytheincreased melt viscosity of the aged PBT powder and reduced crystallinity of SLS parts fabricated from the aged PBT powder. Tensile strength in the z-direction reduced by about 60％ after twice recycling. This conspicuous deterioration of tensile strength in the z-direction is attributed to a decrease in interlayer bonding strength due to increase in the melting viscosity of the aged PBT powder.