An impact absorbing structure for a vehicle including a frame member formed of a resin material, wherein the frame member includes a closed cross sectional portion extending in a vehicle front-rear direction, and a rib protruding at least either upward or downward from the closed cross sectional portion and extending in the vehicle front-rear direction, wherein the frame member includes an inner frame member, and an outer frame member connected to the inner frame member from an outer side in a vehicle width direction, the inner frame member and the outer frame member have an identical shape to each other, and are formed to have a cross section orthogonal to the vehicle front-rear direction opened toward the outer side or an inner side in the vehicle width direction, the inner frame member and the outer frame member are connected in a posture that an opening portion of the inner frame member and an opening portion of the outer frame member face each other, whereby the frame member including the closed cross sectional portion and the rib is formed, wherein each of the inner frame member and the outer frame member includes a frame body opened toward the outer side or the inner side in the vehicle width direction, an upper flange protruding upward from an upper opening edge of the frame body, and a lower flange protruding downward from a lower opening edge of the frame body, the rib includes an upper rib formed by connecting the upper flange of the inner frame member and the upper flange of the outer frame member, and a lower rib formed by connecting the lower flange of the inner frame member and the lower flange of the outer frame member, wherein each of the upper flange and the lower flange includes a flange body (12a1 or 12a2) protruding upward or downward from an opening edge (15u or 15d) of the frame body and extending in a front-rear direction, characterized in that each of the upper flange and the lower flange includes a fastening portion (12b1 or 12b2) protruding upward or downward from a part of the flange body (12a1 or 12a2) in the front-rear direction, a through-hole (12e1 or 12e2) for receiving a fastening member is formed in the fastening portion (12b1 or 12b2), and the through-hole (12e1 or 12e2) is formed in such a way as not to span over a boundary (12c1 or 12c2) between the flange body (12a1 or 12a2) and the fastening portion (12b1 or 12b2). the frame member includes a closed cross sectional portion extending in a vehicle front-rear direction, and a rib protruding at least either upward or downward from the closed cross sectional portion and extending in the vehicle front-rear direction, wherein a closed cross sectional portion extending in a vehicle front-rear direction, and a rib protruding at least either upward or downward from the closed cross sectional portion and extending in the vehicle front-rear direction, wherein the frame member includes an inner frame member, and an outer frame member connected to the inner frame member from an outer side in a vehicle width direction, the inner frame member and the outer frame member have an identical shape to each other, and are formed to have a cross section orthogonal to the vehicle front-rear direction opened toward the outer side or an inner side in the vehicle width direction, the inner frame member and the outer frame member are connected in a posture that an opening portion of the inner frame member and an opening portion of the outer frame member face each other, whereby the frame member including the closed cross sectional portion and the rib is formed, wherein each of the inner frame member and the outer frame member includes a frame body opened toward the outer side or the inner side in the vehicle width direction, an upper flange protruding upward from an upper opening edge of the frame body, and a lower flange protruding downward from a lower opening edge of the frame body, the rib includes an upper rib formed by connecting the upper flange of the inner frame member and the upper flange of the outer frame member, and a lower rib formed by connecting the lower flange of the inner frame member and the lower flange of the outer frame member, wherein each of the upper flange and the lower flange includes a flange body (12a1 or 12a2) protruding upward or downward from an opening edge (15u or 15d) of the frame body and extending in a front-rear direction, that each of the upper flange and the lower flange includes a fastening portion (12b1 or 12b2) protruding upward or downward from a part of the flange body (12a1 or 12a2) in the front-rear direction, a through-hole (12e1 or 12e2) for receiving a fastening member is formed in the fastening portion (12b1 or 12b2), and the through-hole (12e1 or 12e2) is formed in such a way as not to span over a boundary (12c1 or 12c2) between the flange body (12a1 or 12a2) and the fastening portion (12b1 or 12b2).