At the age of sixteen he succeeded his father as village head and continued in that post for the following twelve years. But he and his father joined in censuring the lord of the domain for the harshness of his rule and as a result were imprisoned and later expelled from the domain. In 1870 Tanaka became a minor official in the government of Esashi Prefecture, later a part of Iwate Prefecture. When one of his superior officials was assassinated, he was suspected of having a hand in the affair and was imprisoned for over three years.
In 1884 he was put in prison for opposing an engineering project ordered by Mishima Michitsune, the prefectural governor, which he felt would be too much of a burden on the people of the prefecture.
In the first general election, held in 1890, he was elected to the Lower House of the Diet. In 1891, at the second session of the Diet, he appealed to the government to take measures to combat the pollution caused by the Ashio Mine and thereafter devoted his full energies to this problem. The Ashio Mine, situated in Tochigi Prefecture, was owned and operated by Furukawa Ichibei, the founder of the Furukawa zaibatsu. Poisonous wastes from the mine were dumped into the Watarase River, killing the fish in the river and rendering the farmland in the area unfit for use.