Polyvinyl chloride powder was ground with one of the oxide powders, i.e. CaO, Fe2O3, SiO2 and Al2O3, in air by a planetary ball mill to investigate the mechanochemical dechlorination of PVC. Grinding causes the size reduction of the each component. The PVC powder sample is degraded by grinding with reduction of molecular weight, forming C=C bonds in its structure. The dechlorination occurs in all the ground mixtures, but its phenomenon is classified into two types. One is the solid-phase reaction to form chlorides, CaOHCl and FeCl2 . 2H(2)O, when CaO and Fe2O3 powders are used. The other is the release of HCl gas by degradation when SiO2 and Al2O3 powders are used. All the same, the dechlorination yield increases not only with an increase in grinding time, but also with excess of oxide powder.