A device for the on-line measurement of viscosity and/or level of molten glass, converting the values of these variables into proportional electrical signals. The device comprises one sensor head connected to an electronic control unit and to a data processing unit. The sensor head comprises a fixed metallic core with external fins for air cooling, laid across by two vertical parallel shafts designed for torsional vibration to which are fixed, at the lower extremities, refractory rods partially coated with platinum and, at the upper extremities, the rotors of the two electrical motors which can produce torsional vibration of the vertical shafts. To each shaft are fixed two discs, connected mechanically to the fixed core by three fine rods disposed at 120° angles around the shaft. In operation, the sensor head is installed on a rigid structure fixed over the channel where the molten glass flows, with both rods partially immersed into the melt in order to be protected by the platinum coatings.