Powder Bed Fusion (PBF) is one of the process of Additive Manufacturing. In PBF process, 3D structure is built by repetition of selective melting and solidification of layered metal powder by laser. The melting and solidification process of PBF is depend on specification of metal powder. In this paper, the thermal conductivity of two types of metal powder which have different particle diameter range and bulk density was measured. In addition, the melting process of one-line building was visualized by the high-speed camera and the influence of thermal conductivity on the building characteristics was evaluated. As a result, the deposited metal powder with a high bulk density had high thermal conductivity. Many spatter particles and metallic jets were scattered from the metal powder including the fine particle powders. The thermal conductivity of metal powder also affected the building characteristics.