An upper slewing body to be provided on a lower traveling body of a construction machine so as to be able to slew, the upper slewing body comprising: a bottom plate to be provided on the lower traveling body so as to be able to slew; a pair of vertical plates stood on the bottom plate and extending in a front-rear direction, the vertical plates being opposite to each other in a left-right direction; a boom foot pin attached to the pair of vertical plates so as to straddle the pair of vertical plates, the boom foot pin being attached to the pair of vertical plates so as to be able to be pulled out along an axial direction of the boom foot pin; a boom supported by the boom foot pin so as to be able to rotate with respect to the pair of vertical plates; and a housing box including: a box main body having a housing space formed inside, the housing space including an opening region so as to be open, the box main body allowing an object to be moved in and out of the housing space through the opening region; and an opening/closing lid configured to allow the opening region of the box main body to be opened and closed, wherein the box main body is disposed on a side of one of the pair of vertical plates opposite to the other vertical plate in a state where the boom foot pin is placed opposite the housing space with reference to the opening region in a side view in which the upper slewing body is viewed along the axial direction of the boom foot pin, and the box main body is shaped to open the boom foot pin in the axial direction of the boom foot pin, the opening/closing lid is attached to the box main body so as to be able to rotate with respect to the box main body between a closed position where the opening region is closed and an open position where the opening region is open, characterized in that the opening/closing lid is rotated to the closed position to lie at a position where the opening/closing lid overlaps the boom foot pin in the side view, and is rotated to the open position to lie at a position where the boom foot pin is opened in the axial direction of the boom foot pin. a bottom plate to be provided on the lower traveling body so as to be able to slew; a pair of vertical plates stood on the bottom plate and extending in a front-rear direction, the vertical plates being opposite to each other in a left-right direction; a boom foot pin attached to the pair of vertical plates so as to straddle the pair of vertical plates, the boom foot pin being attached to the pair of vertical plates so as to be able to be pulled out along an axial direction of the boom foot pin; a boom supported by the boom foot pin so as to be able to rotate with respect to the pair of vertical plates; and a housing box including: a box main body having a housing space formed inside, the housing space including an opening region so as to be open, the box main body allowing an object to be moved in and out of the housing space through the opening region; and an opening/closing lid configured to allow the opening region of the box main body to be opened and closed, wherein the box main body is disposed on a side of one of the pair of vertical plates opposite to the other vertical plate in a state where the boom foot pin is placed opposite the housing space with reference to the opening region in a side view in which the upper slewing body is viewed along the axial direction of the boom foot pin, and the box main body is shaped to open the boom foot pin in the axial direction of the boom foot pin, the opening/closing lid is attached to the box main body so as to be able to rotate with respect to the box main body between a closed position where the opening region is closed and an open position where the opening region is open, characterized in that the opening/closing lid is rotated to the closed position to lie at a position where the opening/closing lid overlaps the boom foot pin in the side view, and is rotated to the open position to lie at a position where the boom foot pin is opened in the axial direction of the boom foot pin.