In 1880, Kaneko was appointed as a secretary in the "Genrōin," and in 1884 had joined the Office for Investigation of Institutions, the body organized by the "Genrōin" to study the constitutions of various western nations with the aim of creating a western-style constitution for Japan. The Meiji Constitution that was the product of this committed was promulgated by the Emperor in 1889. Kaneko worked closely with Itō Hirobumi, Inoue Kowashi and Itō Miyoji, and became personal secretary to Itō Hirobumi when the latter became first Prime Minister of Japan. Kaneko was appointed to the House of Peers of the Diet of Japan in 1890, becoming its first Secretary. He was subsequently appointed as Vice Minister, then briefly Minister of Agriculture and Commerce in 1898 in the third Itō administration. He was awarded an honorary doctorate (LL.D.) by Harvard in 1899 for his work on the Meiji Constitution.