An upper frame for a construction machine, comprising a side deck on which a cabin is loaded, the side deck including: a front beam extending laterally of the upper frame and having a left end and a right end; a rear beam extending laterally of the upper frame and having a left end and a right end, the rear beam being positioned rearward of the front beam; a left vertical beam extending longitudinally of the upper frame to interconnect the left end of the front beam and the left end of the rear beam; a right vertical beam extending longitudinally of the upper frame to interconnect the right end of the front beam and the right end of the rear beam; left and right mount holding members (16, 24) attached to a left corner portion formed by the front beam and the left vertical beam and a right corner portion formed by the front beam and the right vertical beam, respectively, so as to be positioned on respective inner sides of the left and right corner portions, to hold respective cabin mounts; and a reinforcement member extending longitudinally of the side deck and having a front end and a rear end, the reinforcement member being joined to an inner lateral surface of a beam to be reinforced, the beam being selected from the left vertical beam and the right vertical beam, characterized in that one of the left and right mount holding members (16, 24) being attached to the beam to be reinforced is a cross allowing member which has a shape avoiding the reinforcement member so as to allow the reinforcement member to extend across the mount holding member longitudinally of the side deck, and the front end of the reinforcement member is directly joined to the front beam while the reinforcement member extends longitudinally across the cross allowing member, wherein the cross allowing member has such a shape that a part thereof on the side of an inner lateral surface of the beam to be reinforced is cut away to allow the reinforcement member to extend longitudinally across the cross allowing member, and the front end of the reinforcement member is joined to the front beam while the reinforcement member extends longitudinally between the cutaway part and the beam to be reinforced. a side deck on which a cabin is loaded, the side deck including: a front beam extending laterally of the upper frame and having a left end and a right end; a rear beam extending laterally of the upper frame and having a left end and a right end, the rear beam being positioned rearward of the front beam; a left vertical beam extending longitudinally of the upper frame to interconnect the left end of the front beam and the left end of the rear beam; a right vertical beam extending longitudinally of the upper frame to interconnect the right end of the front beam and the right end of the rear beam; left and right mount holding members (16, 24) attached to a left corner portion formed by the front beam and the left vertical beam and a right corner portion formed by the front beam and the right vertical beam, respectively, so as to be positioned on respective inner sides of the left and right corner portions, to hold respective cabin mounts; and a reinforcement member extending longitudinally of the side deck and having a front end and a rear end, the reinforcement member being joined to an inner lateral surface of a beam to be reinforced, the beam being selected from the left vertical beam and the right vertical beam, a front beam extending laterally of the upper frame and having a left end and a right end; a rear beam extending laterally of the upper frame and having a left end and a right end, the rear beam being positioned rearward of the front beam; a left vertical beam extending longitudinally of the upper frame to interconnect the left end of the front beam and the left end of the rear beam; a right vertical beam extending longitudinally of the upper frame to interconnect the right end of the front beam and the right end of the rear beam; left and right mount holding members (16, 24) attached to a left corner portion formed by the front beam and the left vertical beam and a right corner portion formed by the front beam and the right vertical beam, respectively, so as to be positioned on respective inner sides of the left and right corner portions, to hold respective cabin mounts; and a reinforcement member extending longitudinally of the side deck and having a front end and a rear end, the reinforcement member being joined to an inner lateral surface of a beam to be reinforced, the beam being selected from the left vertical beam and the right vertical beam,