To effectively remove water impregnated in oil by incorporating an aq. solution having an action to activate water and to decrease the cluster size of water into oil and next, shaking the whole to divide the chain state of the oil molecule into parts by the activated water molecule.

In the case that the shear force of oil is weakened to remove water in the oil at a site or the like, where the oil such as a lubricant is used, the treatment is carried out so as to incorporate an aq. solution having an action to activate water and to decrease the cluster size of water into the oil, and to shake the whole to divide the chain state of the oil molecule into parts by the activated water molecule. In this way, the share force of the oil is weakened and the emulsification, which causes spherical molecule aggregates, is prevented by letting the water molecule activated by the aq. solution enter into the oil molecules to prevent the sticking of the oil molecules to each other. That is, the water molecules and the oil molecules are easily separated from each other and the water molecules existing in the oil is made easily absorbable in the aq. solution to facilitate the removal of water.