EXHAUST GAS TREATMENT UNIT FOR A CONSTRUCTION MACHINE

A cab rear extension beam (14) that is positioned in a front side to a heat exchanger (26) to support a rear side of said cab (28) is provided. The cab rear extension beam (14) includes a rising plate part (14A) that rises from a bottom plate (6), an upper horizontal plate part (14B) that is bent from an upper end of the rising plate part (14A) and extends to the rear side, and a space part (14C) that is formed of the rising plate part (14A) and the upper horizontal plate part (14B), and is formed in a reverse L-letter shape as a whole. A urea water tank (34) is formed with a vertical tank part (35) that is positioned in a rear side and extends in an upper-lower direction and a lateral tank part (36) that extends from a lower part of the vertical tank part (35) to the front side, and is formed in an L-letter shaped vessel as a whole. Besides, the lateral tank part (36) of the urea water tank (34) is disposed in the space part (14C) in the cab rear extension beam (14).