Provided is a frame structure for a vehicle including: a pair of main side rails which extends in the vehicle longitudinal direction and faces each other; and an extension side rail which is connected to a front portion of the main side rail in the vehicle longitudinal direction and extends in the vehicle longitudinal direction, wherein the extension side rail is formed so as to have a substantially C-shaped cross-section and is formed so that a front portion is lower than a rear portion in the vehicle longitudinal direction.