To solve the following problem: in executing clock synchronization using PTP defined in IEEE1588, a traffic of the whole network increases as a result of a synchronization packet being frequently transmitted onto the network by multi-cast.

A clock synchronization device includes: reception means of receiving clock fluctuation information that is information about clock fluctuations; determination means of determining a transmission interval of a synchronization packet transmitted to a transmission source of the clock fluctuation information based on the clock fluctuation information; generation means of generating a synchronization packet; and transmission means of transmitting the generated synchronization packet to the transmission source of the clock fluctuation information at the determined transmission interval.