An upper body of a mobile crane that is fixed to a swing bearing by a bearing bolt and attached to a lower travelling body via the swing bearing, the upper body comprising: a bearing seat surface that is fixed to an upper surface of the swing bearing by the bearing bolt; and a swing frame that includes an intersecting side plate intersecting the bearing seat surface when seen from an up-down direction and is fixed to the bearing seat surface; characterized in that the upper body further comprising: a force dispersing member that is arranged between the intersecting side plate of the swing frame and the bearing seat surface and configured to allow a force transmitted to the bearing seat surface from the intersecting side plate to be dispersed into a plurality of routes, the bearing seat surface including a force dispersion target region, the force dispersion target region including a side-plate intersecting position, in which the bearing seat surface and the intersecting side plate intersect when seen from an up-down direction, and a position located in a vicinity of the side-plate intersecting position, further toward a rear side than a center of revolution of the swing bearing, and in a middle part of the bearing seat surface between two end parts of the bearing seat surface in a bearing radial direction which is a radial direction of the swing bearing, the force dispersing member including at least one vertical plate extending in an up-down direction, and the at least one vertical plate being fixed to a region of the bearing seat surface other than the force dispersion target region. a bearing seat surface that is fixed to an upper surface of the swing bearing by the bearing bolt; and a swing frame that includes an intersecting side plate intersecting the bearing seat surface when seen from an up-down direction and is fixed to the bearing seat surface; characterized in that the upper body further comprising: a force dispersing member that is arranged between the intersecting side plate of the swing frame and the bearing seat surface and configured to allow a force transmitted to the bearing seat surface from the intersecting side plate to be dispersed into a plurality of routes, the bearing seat surface including a force dispersion target region, the force dispersion target region including a side-plate intersecting position, in which the bearing seat surface and the intersecting side plate intersect when seen from an up-down direction, and a position located in a vicinity of the side-plate intersecting position, further toward a rear side than a center of revolution of the swing bearing, and in a middle part of the bearing seat surface between two end parts of the bearing seat surface in a bearing radial direction which is a radial direction of the swing bearing, the force dispersing member including at least one vertical plate extending in an up-down direction, and the at least one vertical plate being fixed to a region of the bearing seat surface other than the force dispersion target region. a force dispersing member that is arranged between the intersecting side plate of the swing frame and the bearing seat surface and configured to allow a force transmitted to the bearing seat surface from the intersecting side plate to be dispersed into a plurality of routes, the bearing seat surface including a force dispersion target region, the force dispersion target region including a side-plate intersecting position, in which the bearing seat surface and the intersecting side plate intersect when seen from an up-down direction, and a position located in a vicinity of the side-plate intersecting position, further toward a rear side than a center of revolution of the swing bearing, and in a middle part of the bearing seat surface between two end parts of the bearing seat surface in a bearing radial direction which is a radial direction of the swing bearing, the force dispersing member including at least one vertical plate extending in an up-down direction, and the at least one vertical plate being fixed to a region of the bearing seat surface other than the force dispersion target region.