UPPER SLEWING BODY OF CONSTRUCTION MACHINE

To arrange a terminal box while suppressing a decline in degree of freedom of layout of devices. An upper slewing body 3 includes: a bottom plate 21 rotatably attached to a lower traveling body 2; supporting frames 22A and 22B standing on the bottom plate 21; an engine 14 supported on the bottom plate 21 by the supporting frames 22A and 22B; a generator motor 15 connected to the engine 14; and a terminal box 18 including a terminal T, which is electrically connected to the generator motor 15 and allows a cable C2 to be connected, and a box main body housing the terminal T and being attached to the generator motor 15. The generator motor 15 includes a facing section 15a facing the bottom plate 21 at a position separated from the supporting frames 22A and 22B in a plan view. The terminal box 18 is arranged between the facing section 15a of the generator motor 15 and the bottom plate 21.