Poly(3,4-ethylenedioxythiophene) (PEDOT) grains were synthesized by solvent-free chemical oxidative polymerization in one-step and one-pot manner. The resulting PEDOT grains had atypical shapes with a volume-average diameter of 57 +/- 45 mu m and showed an electrical conductivity of 1.9 x 10(-3) S cm(-1). Furthermore, it was clarified that the PEDOT grains showed light-to-heat photothermal property.