A transmission device (100) outputs an accumulation amount of packets of a first transmission buffer immediately before a packet is written into the first transmission buffer (105), to a reception device (200). A first reception buffer amount read-out unit (206) of the reception device reads out the amount of the packets accumulated in the first reception buffer immediately before the packet is read out from the first reception buffer. An accumulated amount addition unit (207) adds the amount of packets accumulated in the first transmission buffer and the amount of packets accumulated in the first reception buffer. A correction unit (208) adjusts the oscillation frequency of a variable frequency oscillator of a reception time stamp timer (209) so that the added value is constant.