The electrochemical and magnetic properties of polyazulene have been studied by electrochemical cyclic voltammetry and ESR. Two pairs of oxidation and reduction peaks have been observed in the cyclic voltammogram which indicates that reversible p-type doping. The anomalous behavior of the spin susceptibility χ upon electrochemical doping, associated with these redox peaks in the cyclic voltammogram, has been revealed by the in situ measurement; the extraordinary large χ= c a . 4 ×10 -5 emu/mol in the neutral state once decreases upon doping to 2 ×10 -5 emu/mol at several mol% and then increases up to c a . 7 ×10 -5 emu/mol corresponding to the as-grown state at c a . 25 mol%, and then decreases again at higher doping levels. These results can be interpreted as two-stages doping (oxidation) process into polyazulene with a unique band structure.