A method for transmitting pieces of synchronized picture data having the same data length of which each include a synchronizing signal, an identifying code, pieces of compressed picture data having different data lengths and an error correcting code in that order is disclosed. To correctly decode each of the compressed picture data, it is required to start an decoding operation from a head address of each of the compressed picture signal. Therefore, in cases where a head address of a piece of compressed picture data exists in a piece of synchronized, an existence information flag for informing the existence of the head address, an address pointer for indicating an address of the head address, and a block number for indicating a position of the compressed picture data having the head address are added just after the identifying code to correctly decode the compressed picture data and other pieces of following compressed picture data in the synchronized picture data. In contrast, in cases where any head address does not exists, a no-existence information flag for informing the no-existence of the head address is merely added just after the identifying code.