Conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) has been synthesized by solid-state polymerization of 2,5-diiodo-3,4-ethylenedioxythiophene under normal conditions. The resulting iodine-doped PEDOT is completely insoluble in common organic solvents and retained partial crystal structure of monomer as indicated by scanning electron microscopy. Electrical conductivity measurement showed that PEDOT exhibited conductivity in the range of 0.16–0.23 S/cm (pressed powder pellet) with temperature dependence. Thermogravimetric and differential thermal gravimetric analysis of PEDOT indicated that its main chain was stable up to ca. 200 °C.