The objective of construction machinery of the invention is to reduce noise transmitted to a driving cab and to improve bond strength of a beam to a central framework and a lateral framework. A driving cab support beam (23) which supports the driving cab (7) is formed by using a lower beam (23A), an upper beam (23B), a back longitudinal beam (23C) and an opening (23D) in form of transverse U shaped cross section with an opening in front side. Therefore, seal space is not formed in the driving cab support beam, which is able to prohibit the noise generated by engine etc. from being enhanced due to resonance in the driving cab support beam. In addition, the opening (23D) of the driving cab support beam (23) is configured by way of facing the opening in front side of the driving cab support frame (20), which is able to enhance the bond strength of rear side of the driving cab support beam (23) adjacent to a counterweight (5) and to enhance the bond strength of the driving cab support beam (23) to a left longitudinal plate (14) and a left framework (18) of the central framework (12).