A quick connecting device and a shower room assembly are disclosed. The quick connecting device comprises an inserting member, a receiving member and a locking key. The inserting member comprises a sheet-like first body, the first body including a first connecting surface configured to fixedly connect an end surface of a corner end of a first track, a first main surface opposite to the first connecting surface, and a columnar insert extending outwards from the first main surface, a first keyway formed on a surface of the columnar insert. The receiving member comprises a sheet-like second body, the second body including a second connecting surface configured to fixedly connect an end surface of a corner end of a second track, a second main surface opposite to the second connecting surface, and a receiver extending outwards from the second main surface, the receiver being provided with a receiving chamber in clearance fit with the columnar insert and the receiver being provided with a second keyway therein. The locking key is configured such that when the columnar insert is inserted into the receiving chamber and the first and second keyways are in a matched state, the locking key restricts exiting of the columnar insert from the receiving chamber. The shower room assembly comprises a track connected at a corner uses the above quick connecting device.