A quick connecting device configured to connect a track of a shower room assembly at a corner, comprising: an inserting member comprising 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 being formed on a surface of the columnar insert; a receiving member including 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; and a locking key configured such that when the columnar insert is inserted into the receiving chamber so that the first and second keyways are in a matched state, the locking key restricts exiting of the columnar insert from the receiving chamber; wherein the first keyway has a circular segment-shaped cross section; the second keyway has a circular segment-shaped cross section; the two cross sections form a complete circle when the first and second keyways are matched; and the locking key is a cylindrical key including a hand-held portion external to a locking orifice and a key body at an intermediate portion thereof, a cross section of the key body being in the same shape with that of the cross section of the second keyway, wherein the locking key is rotatably supported on the locking orifice to allow the columnar insert to be inserted into the receiving chamber and restrict the exiting of the columnar insert from the receiving chamber by rotating. an inserting member comprising 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 being formed on a surface of the columnar insert; a receiving member including 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; and a locking key configured such that when the columnar insert is inserted into the receiving chamber so that the first and second keyways are in a matched state, the locking key restricts exiting of the columnar insert from the receiving chamber; wherein the first keyway has a circular segment-shaped cross section; the second keyway has a circular segment-shaped cross section; the two cross sections form a complete circle when the first and second keyways are matched; and the locking key is a cylindrical key including a hand-held portion external to a locking orifice and a key body at an intermediate portion thereof, a cross section of the key body being in the same shape with that of the cross section of the second keyway, wherein the locking key is rotatably supported on the locking orifice to allow the columnar insert to be inserted into the receiving chamber and restrict the exiting of the columnar insert from the receiving chamber by rotating.