Right and left floor panel support mechanisms (40) and (46) are provided on a revolving frame (5) to support a front end of a floor panel (21) pivotally for permitting tilt-up and tilt-down of the floor panel (21). A tilting mechanism (54) is provided between the revolving frame (5) and the floor panel (21) for tilting the floor panel (21) together with a canopy (31). Through a plural number of vibration insulators (20), a floor panel mount plate (19) is mounted on a support member (12) which is located in a rear side portion of the revolving frame (5). A housing mount plate (24) of the floor panel (21) and a base plate (37) of the canopy (31) are detachably fixed to the floor panel mount plate (19) by the use of fastening bolts (39). After removing the fastening bolts (39), the floor panel (21) and canopy (31) can be tilted together without necessitating to disassemble the vibration insulators (20).