An object is to suppress vehicle body deformation in a side collision without sacrificing a vehicle interior space.Provided is a first reinforcing member 10 disposed in a locker 12 at a vehicle lateral direction inner side, and a second reinforcing member 20 disposed in locker 12 at a vehicle lateral direction outer side, which opposes first reinforcing member 10 in a vehicle lateral direction, and which is provided with a side surface 20A and an end surface 20E (engaging portions) that engage with first reinforcing member 10 when locker 12 deforms. When locker 12 begins to deform due to a side collision to a vehicle 18, end surface 20E of second reinforcing member 20 contacts and engages flange 10E of first reinforcing member 10, and a torsional deformation can be suppressed, and side surface 20A contacts flange 10D, and a crushing deformation of locker 12 in a vehicle lateral direction can be suppressed. Since first reinforcing member 10 and second reinforcing member 20 are provided in locker 12, vehicle interior space is not sacrificed.