There are provided a content data transmission method, device, and program that minimize serious disturbances in reproduced content on the reception side, caused by a transmission error of encoded data, without sending feedback information from the reception side to the transmission side. When an encoder creates encoded data to be distributed, the encoder creates plural items of encoded data at the same time or creates FEC data at the same time in advance and, when storing the data in a file, stores the data as if the data were one item of encoded data. When a distribution server distributes the data using the file, the plurality of items of encoded data are automatically distributed at the same time and the FEC data is distributed. A client receives the plurality of items of encoded data or the FEC data to reduce the probability of data shortage due to a packet loss and, as a result, the deterioration in the image quality and the audio quality is reduced.