To lower a deformation amount of an upper frame by efficiently transmitting an input from a suspension to the upper frame.

This vehicle body side part structure has a rear suspension mount bracket part 7, a rear wheel house part 13, and a rear pillar part 15 integrally formed. In this case, the rear suspension mount bracket part 7 is formed so as to be thicker than the other part, and the rear pillar part 15 includes a part of the periphery of a door of a rear fender and is composed of outer walls 21 and the like, an inner wall 23, and vertical walls. This structure is also provided with horizontal ribs for connecting the vertical walls with each other in a front-to-back direction of a vehicular body, vertical ribs 41 and the like for connecting the rear suspension mount bracket part 7 with the rear pillar part 15 so as to be laid across up and down, and a connection rib 45 for connecting the vertical ribs 41 and the like with each other in the front-to-back direction of the vehicular body.