A transmission device comprising: a communication unit performing communication with one or more receiving devices; a distance measurement unit measuring direct distances to the respective receiving devices; a transmission data setting unit setting transmission data including content data including audio to be transmitted and time information indicating the time when reproduction of content data is started by the transmission device with respect to the respective receiving devices distances of which are measured based on the measured distances to the respective receiving devices; and a transmission processing unit transmitting transmission data set by the transmission data setting unit to corresponding receiving devices of transmission targets all at once, wherein the transmission data setting unit is configured to set time when the transmission device starts reproduction of the content data as a reference time, and set the time information for synchronizing audio indicated by the content data reproduced in the transmission device with audio indicated by the content data reproduced in the receiving devices with respect to each receiving device using the set reference time as a reference; wherein, when the communication unit configured to receive an adjustment signal for changing the device to be the reference of time when the reproduction of content data is started, the transmission data setting unit sets the time when the receiving device which has transmitted the adjustment signal starts reproduction of content data as a reference time, and sets the time when the transmission device starts reproduction of the content data and the time information with respect to the respective devices using the reference time set based on the adjustment signal as a reference. a communication unit performing communication with one or more receiving devices; a distance measurement unit measuring direct distances to the respective receiving devices; a transmission data setting unit setting transmission data including content data including audio to be transmitted and time information indicating the time when reproduction of content data is started by the transmission device with respect to the respective receiving devices distances of which are measured based on the measured distances to the respective receiving devices; and a transmission processing unit transmitting transmission data set by the transmission data setting unit to corresponding receiving devices of transmission targets all at once, wherein the transmission data setting unit is configured to set time when the transmission device starts reproduction of the content data as a reference time, and set the time information for synchronizing audio indicated by the content data reproduced in the transmission device with audio indicated by the content data reproduced in the receiving devices with respect to each receiving device using the set reference time as a reference; wherein, when the communication unit configured to receive an adjustment signal for changing the device to be the reference of time when the reproduction of content data is started, the transmission data setting unit sets the time when the receiving device which has transmitted the adjustment signal starts reproduction of content data as a reference time, and sets the time when the transmission device starts reproduction of the content data and the time information with respect to the respective devices using the reference time set based on the adjustment signal as a reference.