LOWER VEHICLE-BODY STRUCTURE OF VEHICLE

[Problem] An object is to provide a lower vehicle-body structure of a vehicle capable of maintaining a support effect for a side sill by a front-rear extended portion even at the time of a side collision.[Means for Solution] A lower vehicle-body structure 100 of a vehicle includes: a floor panel 2; a side sill 50; and a frame member 20 that extends in the front-rear direction on the vehicle-width-direction inner side of the side sill 50 and includes a front-rear extended portion 22 that is in abutment against the side sill 50 on the vehicle-width-direction inner side and extends in the vehicle front-rear direction along the side sill 50. The front-rear extended portion 22 includes: a bottom face portion 41 that faces the floor panel 2 from below; an inner wall portion 42 that extends toward the floor panel 2 from an inner end portion of the bottom face portion 41 in the vehicle width direction; and an innerside flange 44 that extends to the vehicle-width-direction inner side from a distal end portion of the inner wall portion 42 and is joined to the floor panel 2. Deformation facilitating portions 48, 49 that facilitate deformation of the bottom face portion 41 in the vehicle width direction when a collision load in the vehicle width direction is input are formed in the bottom face portion 41.