Abstract: Reciprocal attitude angle self-differentiating device (10) for pivotable wheels (11,12;110) of handtrucks, each of the wheels (11,12;110) being respectively rotatably mounted about a substantially horizontal axis (22,23;220) belonging to a wheel supporting body (21,15;210), the body (21,15;210) being rotatably mounted about a substantially vertical axis (29,30;290), in which at least one pair of wheels belonging to the handtruck being mutually coupled by means of a device (10) comprising:a) a first coupling mechanism (14), cooperating with the supporting body (15) of the first (12) of the wheels belonging to the pair;b) a second coupling mechanism (13,25;130,250) freely movable mounted on the supporting body (21;210) of the second wheel (11;10) belonging to the pair of wheels, the second mechanism (13,25;130,250) cooperating with a third mechanism (16,24;240) integral and rigidly connected with the supporting body (21;210) of the second wheel (11;110);c) a fourth, motion transmitting, mechanism (20), cooperat