A time synchronization system , comprising: a plurality of wireless terminal devices , each having a first real-time clock ; and a control device having a second real-time clock of which the number of effective figures per clocking is greater than that of the first real-time clock, wherein the control device includes: a preset time determinator for determining a preset time to be set to the first real-time clock of the wireless terminal device based on the second real-time clock; and a latency time calculator for calculating the latency time, the latency time being a period of time from the wireless terminal device acquiring the preset time until the preset time being set to the first real-time clock, and the latency time being calculated in a clock accuracy having the number of effective figures greater than that of the first real-time clock, by subtracting a time required for the wireless terminal device to acquire the preset time from the preset time, wherein the plurality of terminal devices include: a latency time timer for clocking a lapse of a latency time based on said latency time calculated by said latency time calculator ; and a time setter for setting the preset time to the first real-time clock when the latency time is lapsed, wherein the control device transmits the latency time and the preset time to the wireless terminal devices in decreasing order of the number of hops from the control device. a plurality of wireless terminal devices , each having a first real-time clock ; and a control device having a second real-time clock of which the number of effective figures per clocking is greater than that of the first real-time clock, wherein the control device includes: a preset time determinator for determining a preset time to be set to the first real-time clock of the wireless terminal device based on the second real-time clock; and a latency time calculator for calculating the latency time, the latency time being a period of time from the wireless terminal device acquiring the preset time until the preset time being set to the first real-time clock, and the latency time being calculated in a clock accuracy having the number of effective figures greater than that of the first real-time clock, by subtracting a time required for the wireless terminal device to acquire the preset time from the preset time, a preset time determinator for determining a preset time to be set to the first real-time clock of the wireless terminal device based on the second real-time clock; and a latency time calculator for calculating the latency time, the latency time being a period of time from the wireless terminal device acquiring the preset time until the preset time being set to the first real-time clock, and the latency time being calculated in a clock accuracy having the number of effective figures greater than that of the first real-time clock, by subtracting a time required for the wireless terminal device to acquire the preset time from the preset time, wherein the plurality of terminal devices include: a latency time timer for clocking a lapse of a latency time based on said latency time calculated by said latency time calculator ; and a time setter for setting the preset time to the first real-time clock when the latency time is lapsed, a latency time timer for clocking a lapse of a latency time based on said latency time calculated by said latency time calculator ; and a time setter for setting the preset time to the first real-time clock when the latency time is lapsed, wherein the control device transmits the latency time and the preset time to the wireless terminal devices in decreasing order of the number of hops from the control device. <EOS>