Disclosed is a submerged-type compact filtration apparatus of minimized footprint which can be installed easily, maintained safely and conveniently, and operated with substantially reduced energy. The submerged-type filtration apparatus of the invention comprises a filtration bath disposed over a ground; a filtration membrane cassette configured to be installed in the filtration bath; and a first guide disposed in the filtration bath and configured to guide the filtration membrane cassette when the filtration membrane cassette is inserted into the filtration bath so as to be installed therein.