In a vehicle frame structure, upper ends of a front frame and a rear frame, which connect a lower frame and an upper frame vertically, are connected to each other above the upper frame, and a front portion frame assembly is connected to a main frame assembly via the lower frame and the upper ends of the front and rear frames. A bumper includes a front-rear frame portion extending forward from the front frame, and an inclined frame portion arranged between an intermediate portion of the front frame and an end portion of the front-rear frame portion. The bumper includes a sub-bumper, the sub-bumper including a front sub-frame extending upward from a front end of the bumper, and a front-rear sub-frame connected between an end portion of the front sub-frame and an intermediate portion of the front frame above the upper frame.