PURPOSE: To provide a polyaniline having excellent properties such as a sufficiently high molecular weight, a relatively narrow molecular weight distribution and a high solubility in an organic solvent by using inexpensive hydrogen peroxide as the oxidizing agent and a very small amount of a transition metal and/or its compound as the catalyst and to provide a new process for producing it.

CONSTITUTION: Hydrogen peroxide is added to a solution comprising 1mol of aniline and/or its derivative, 0.0001-0.01mol of a transition metal or its compound and a solvent, and the entire mixture is subjected to oxidative polymerization to obtain a soluble polyaniline which has a solubility of 50g/l or above in N-methylpyrrolidone, a solubility of 25g/l or above in dimethylformamide, a number-average molecular weight (Mn) of 1000 or above, a polydispersity index (Mw/Mn) of 5.0 or below and a conductivity of 10-3 to 102Scm-1 when doped with a proton acid of a pKa value of 3.0 or below.