Provided are an apparatus and method for upstream transmission of variable bit rate traffic in a Hybrid Fiber Coaxial (HFC) network. The apparatus includes: a VoIP signal processing unit for digitizing a voice of a speaker to create a voice packet, detecting a mute section to suppress packet generation, and generating an Service identification (SID) packet in the mute section; a storage unit for storing the voice packet and the SID packet created by the VoIP signal processing unit and notifying information on the stored packets; a VoIP activity determining unit for determining a voice activity based on the information on the stored packets notified from the storage unit; and a packet processing unit for including the voice activity transferred from the VoIP activity determining unit in the packets from the storage unit to encapsulate them and transmit it to a network device.