A novel catalytic decomposition of H2O to stoichiometric Hz and O-2 using mechanical energy was studied. The mechano-catalytic decomposition of H2O proceeded on some oxide powders when they were suspended in distilled water by magnetic stirring. Mechanical energy to decompose H2O was supplied by rubbing of oxide powders between the bottom of Pyrex glass reaction vessel and the stirring rod. H2O decomposition was revealed to take place essentially by the friction of oxide powder with the bottom surface of the reaction vessel.