Abstract: In a liquid treating process according to the present invention, colloidal particles in stable hydrated states or in meta-stable hydrophobic colloidal states in a liquid are rendered hydrophobic and separated from liquid molecules by an electric field formed by a microwave. The separated colloidal particles are allowed to collide against one another to become flocculated under a cavitation effect by a ultrasonic wave having a frequency in a low frequency range, and the liquid is deodorized by an electromagnetic ultrasonic wave having a frequency in a high frequency range. Therefore, it is possible to easily and reliably remove the colloidal particles dissolved in the liquid and to deodorize the liquid without need for a large-scaled equipment.