Discussed is an apparatus for transmitting an encoded video stream, comprising: a slice generating unit that divides a frame, comprised in a video stream, into at least one or more slice; and a transmitting unit transmitting the slice in units of a packet within a slice deadline, which is a time limit required for transmission of the slice, the transmitting unit that preferentially transmits a header packet that contain a slice header information over other packets, and the slice header that comprises of information necessary for reconstructing the slice, wherein the transmitting unit comprises: a packet transmitter that retransmits the packet when the packet fails to be transmitted within the predetermined retry limit; and a header protector performing control for the header packet to be repeatedly transmitted within the slice deadline even when number of retransmissions of the header packet exceeds the predetermined retry limit.