The government official of "the Tsushima Clan" joined "delegation from the Korean Yi dynasty", and has kept a record ofthe voyage by making "a diary on board." By investigating the record, the voyage of those days in the "sea route" from Pusan to Osaka could be known. In this research, the contents of "the diary on board of the Chosen Tushinshi" which are record of the 11th "delegation from the Korean Yi dynasty" in 1748 arc analyzed. As for "the diary on board of the Chosen Ttrshinshi", the voyage from Osaka Kawaguchi to Katsumoto in Iki, July 4 to July 17, was recorded by the lunar calendar of those days. The content showed the port called by "delegation from the Korean Yi dynasty" and the time spent on the voyage. And the distance of the voyage was able to be found from the present chart, and also the speed could be guessed. So we can Buess the voyage and current of those days by investigating "current data",by "Maritime Safety Agency", which showed current of those days.