The present invention relates to an on-board device for measuring the mass and the position of the center of gravity of an aircraft having a plurality of landing gears (T1, T2), each landing gear (T1, T2) being provided with at least one contact member (2) having a deformable element (3) that is deformable under the action of the weight of the aircraft when the aircraft is standing on a surface, and is remarkable in that the formable element (3) is provided with a bar (4) having an eddy current sensor (6) at its free end.