This pager intends to examine the correspondence between Kaneko Kentaro and Herbert Spencer during Kaneko's stay in London in August 1892. Duncan's “Life and Letters of Herbert Spencer” includes three letters of Spencer to Kaneko dated 21st, 23rd and 26th of August, 1892, and London University Library holds a letter of Kaneko to Spencer dated 24th of August, 1892.In these letters, Spencer gave Kaneko very conservative advices, for example, house holder's suffrage, restriction of the National Assembly's function to the non-coercive advice to the government and to prohibition of the foreigner's rights to hold land, to work mines and to engage the coasting trade. He even declared that Japanese government gave “too large an instalment of freedom.” Though it seems curious that Spencer whose books inspired the people's rights movement gave to the Japanese Statesman such a “conservative advice”, it seems to be possible to imagine that Spencer was influenced by the opinion of Mori Arinori, who was intimate with him as a Japanese minister. Mori's draft of Japanese constitution written in 1884 includes some conservative views which Spencer advised to Kaneko eight years later. This paper aims to prove this estimation by examining Mori's views on constitution. Spencer was not a unconditional liberalist, but a gradualist who believed that a political institutions ought to fit to the each stage of social evolution. It seems possible to believe that when he was told by Mori on the low stage of Japanese social evolution, his conservative advices to Japanese government. naturally followed.This paper also includes an examination of the political thought of Baba Tatsui who as an ardent Spencerian, tried to utilize Spencer's theory of social evolution to support the people's rights movement, and a reference to the comments on Spencer's letters by Lafcadio Hearn, who heartly agreed with Spencer's advices to Kaneko.