The present invention discloses an apparatus and a method for transmitting a packet and an apparatus and a method for receiving a packet, based on a timing model of an MPEG media transport (MMT) system, which is integrated by considering the advantages of a timing model in an MPEG-2 system and an RTP timing model. The apparatus for transmitting the packet transmits the packet from the MMT system, and comprises: a video stream that is encoded based on an input picture; and an MMT packetizing portion for generating the MMT packet by packetizing an audio stream that corresponds to the video stream, wherein the MMT packetizing portion generates the MMT packet by including synchronization information, which is generated based on a system time clock (STC) that is a master program clock for a video and audio encoder, and an MMT buffering delay. As a result, synchronization of various media sources, measurement of a packet arrival jitter, as well as STC clock locking of the apparatus for transmitting and the apparatus for receiving the MMT can be achieved.