An upper slewing body for use in a construction machine, the upper slewing body configured to be mounted on a lower travelling body of the construction machine so as to be slewable and comprising: an upper frame including a left side portion and a right side portion; a cab mounted on one of the left side portion and the right side portion, the cab including a bottom frame constituting a bottom wall of the cab, a plurality of pillars, and an entrance opening on an outer side of the upper frame, the plurality of pillars including an outer pillar located on a side where the entrance opening exists; an antivibration mount for suppressing a vibration of the cab; and a displacement restrainer (20, 22) for limiting a relative displacement of the cab with respect to the upper frame in a direction of rising away from the upper frame to a specific amount or less; wherein the displacement restrainer (20, 22) includes a penetrating member, characterized in that each of the plurality of pillars has a lower end joined to an upper surface of the bottom frame to thereby allow the pillar to stand on a periphery of the cab, a reinforcing member is attached to the lower end of the outer pillar to reinforce the joint between the lower end and the bottom frame, the penetrating member vertically penetrates the reinforcing member and the bottom frame and is secured to the upper frame, the displacement restrainer (20, 22) and the reinforcing member include respective load transmitting surfaces vertically opposed to each other so as to transmit a load to each other at a position above the joint between the bottom frame and the outer pillar when the cab is displaced in the rising direction by the specific amount or more. an upper frame including a left side portion and a right side portion; a cab mounted on one of the left side portion and the right side portion, the cab including a bottom frame constituting a bottom wall of the cab, a plurality of pillars, and an entrance opening on an outer side of the upper frame, the plurality of pillars including an outer pillar located on a side where the entrance opening exists; an antivibration mount for suppressing a vibration of the cab; and a displacement restrainer (20, 22) for limiting a relative displacement of the cab with respect to the upper frame in a direction of rising away from the upper frame to a specific amount or less; wherein the displacement restrainer (20, 22) includes a penetrating member, characterized in that each of the plurality of pillars has a lower end joined to an upper surface of the bottom frame to thereby allow the pillar to stand on a periphery of the cab, a reinforcing member is attached to the lower end of the outer pillar to reinforce the joint between the lower end and the bottom frame, the penetrating member vertically penetrates the reinforcing member and the bottom frame and is secured to the upper frame, the displacement restrainer (20, 22) and the reinforcing member include respective load transmitting surfaces vertically opposed to each other so as to transmit a load to each other at a position above the joint between the bottom frame and the outer pillar when the cab is displaced in the rising direction by the specific amount or more.