A knee protector structure comprises a transverse frame member extending in the transverse direction of a vehicle body below an instrument panel provided in front of the front seat, a center bracket an upper portion of which is connected to a body panel in front of the front seat substantially at the middle between right and left sides and a lower portion of which is connected to the floor of the vehicle body. The frame member is connected to the cabside at an outer end portion and to the center bracket at an inner end portion. A knee pad is supported by a bracket member connected to the frame member at a front end portion and to the knee pad at a rear end portion.