Ueda Akinari, a man of letter of Edo-era in the 18th century of Japan, is a famous writer of Yomihon and an well-known nativist scholar, whereas his Haikai works has not been researched much. In the mean time, precedent studies found very few of Haikai interchanges made by Akinari and Buson, at most simply mentioning the memorial phrase written by Akinari honoring Buson. To probe aspects of interchanges between Akinari and Buson, this study contemplated the effects of the interchanges to the world of their works, mainly focusing on the elegy to Buson and critical review of foreword that Buson sent for a work of Akinari. As a result of the contemplation, we can say that Akinari understood Buson's haikai had been based on Basyo's haikai through the elegy for Buson sent by Akinari, and he highly praised Buson's achievements of great Haikai works especially with his deep knowledge of Chinese poetry. Meanwhile, Buson's evaluation of Akinari could be found in his letters and others. He understood well non-secular character of Akinari and estimated high Haikai works of Akinari. As we probed how such mental interchanges of two men of letters affected Haikai works in reality, we could find a phrase similar with Buson's in the Haikai works of Akinari, which he wrote being conscious of Buson's Haikai. Also, in Haikai works of Buson, the existence of phrases influenced by Akinari's works like Yomihon and Asajigayado in Ugetsu Monogatari could pointed out.