Obtained is a vehicle body skeleton structure having increased rigidity achieved without making the structure complex.A skeleton body comprises a rocker rear, a rear pillar, and a rear wheel house which are joined together. An inner corner portion which forms a rocker reinforcement is formed on the inner side of a bent portion located near the joint portion. A bulging portion having a three-dimensional curved surface shape bulging in a convex shape is formed at the inner corner portion. The rocker reinforcement is formed in such a manner that an upper wall portion, an upper end flange portion, and a rear end standing wall portion are formed on the inner side of the bent portion so as to be directed in three directions and so as to continue to the bulging portion at a position at which the upper wall portion, the upper end flange portion, and the rear end standing wall portion surround the bulging portion. Also, the upper end flange portion is joined to both a rocker inner panel and a pillar inner panel, and the rear end standing wall portion is joined to a wheel house outer panel.