FIELD: measuring equipment. SUBSTANCE: invention relates to non-destructing control of mechanical stresses in ferromagnetic materials; it can be used for organization of active monitoring of a stress-strain state of metal structures of different construction and environmentally hazardous facilities, as well as for the creation of smart and intelligent construction objects. The device contains a magnet sensor consisting of two measuring windings, magnetic circuits with a square cross-section, located mutually perpendicular, exciting sensor winding placed on two combined poles of magnetic circuit cores, and a measuring unit. The device additionally contains a high-frequency AC generator connected to exciting windings, combined poles of magnetic circuit cores of which are placed symmetrically, and the measuring unit is made in the form of sequentially connected rectifiers with low pressure drop on operational amplifiers, an analogue-to-digital converter, a processor, a unit for data transmission via a wireless interface, and it is connected to measuring windings. EFFECT: increase in the accuracy and sensitivity of measurements, as well as the possibility of fixation of fast transitional processes. 1 cl, 2 dwg.