Overload safety device for telescopic cranes includes transmitter means for registering a working radius of a crane jib having a base jib member and transmitter means for registering a load applied to the jib, analog computer means operatively connected to both the first and second transmitter means for comparing a nominal value predetermined by the working radius with actual values furnished by the transmitter means for registering the load, and signal means responsive to a condition wherein the actual values equal the nominal value for releasing an overload signal, the nominal values being proportional to a permissible limit moment for a respective working radius, the permissible limit moment being composed of a moment of the jib weight and a moment for the permissible load, the transmitter means for registering the load being mounted at the base jib member of the crane jib and being adapted to measure the bending moment of the base jib member, the transmitter means for registering the load being an elongation measuring transmitter.