A filtration apparatus having one or more upright tubular filter elements having a surface coated with a pre-coat layer of a filter aid through which a liquid is filtered. Different from conventional apparatuses, the filter element of the present invention is provided with a gas exhaust tube or liquid drain tube connected to the upper or lower part of the filter element, respectively. By virtue of this means, the liquid used for forming the pre-coat layer as the suspension medium can be completely discharged out of the apparatus prior to introduction of the liquid to be filtered so that the liquid in the apparatus can be switched from the pre-coat forming liquid to the filtered liquid without producing a mixture thereof, and without causing defects in the pre-coat layer.