A data broadcasting system is provided which is capable of achieving display intended and desired by a provider of data broadcasting contents. The data broadcasting system includes a transmitting system and a receiver. The transmitting system includes an HD (High Definition)/SD (Standard Definition) converting section to convert HDTV (High Definition Television) data contents into data contents having a resolution applicable to an SDTV (Standard Definition Television) monitor to obtain SDTV data contents and a multiplexing section to multiplex the SDTV data contents, HDTV video contents, and HDTV data contents. The receiver has a multiplexing separation section to separate the data broadcasting contents received from the transmitting system into the SDTV data contents, the HDTV video contents, and the HDTV data contents, a down-scaling section to convert a resolution of the HDTV video contents into a resolution applicable to the SDTV monitor to obtain SDTV video contents, and a video/data synthesizing section to synthesize the SDTV video contents and the SDTV data contents to obtain display data to be used in the SDTV monitor.