The present invention provides a floor through-passage molding apparatus adapted for a floor construction, which comprises a forming sleeve, a first covering plate assembly, a second covering plate assembly and a plurality of retaining assemblies. Said forming sleeve has a sleeve wall defining a hollow channel, a first opening and a second opening. Said first and second covering plate assemblies are respectively disposed on the first and second openings of said forming sleeve. Said plurality of retaining assemblies passes through the hollow channel of said forming sleeve, and are respectively retained with the first and second covering plate assemblies by a plurality of corresponding retaining holes formed on said first and second covering plate assemblies, wherein positions of the plurality of corresponding retaining holes distributed on said first covering plate assembly or said second covering plate assembly jointly define at least one plane.