A method and apparatus for completion mechanism for transmission using preconfigured uplink resource (PUR) in a wireless communication system is provided. While in a radio resource control (RRC) idle state and/or an RRC inactive state, a wireless device configured to operate in a wireless communication system i) performs uplink (UL) data transmission using a preconfigured uplink resource (PUR) to a network, ii) attempts to acquire downlink (DL) information on a physical downlink shared channel (PDSCH) from the network, and iii) based on the DL information including only timing advance command (TAC) media access control (MAC) control element (CE), considers that the UL data transmission using the PUR is successful.