A suspension frame structure with which a high rigidity can be obtained with respect to load applied from suspension arms and an engine mount is provided. In a suspension frame structure according to the present invention, a suspension frame includes a right front fixing portion, a left front fixing portion, a right rear fixing portion and a left rear fixing portion to which a right suspension arm and a left suspension arm are fixed, contours of the right extension bracket and the left extension bracket on an interior side of a vehicle extend along an circular arc-shaped locus that connects side member fixing positions and an engine mount attachment portion, as viewed from an upper side of a vehicle, and tangents at front ends of the contours respectively pass through arm fixing positions.