PURPOSE: To improve water proofness and moisture proofness so as to keep the electrical insulation between a resistance element and an object to be measured for a long period.

CONSTITUTION: The strain gauge is provided with a resistance element 5 that is bonded on the upper surface of a gauge base 3 by an adhesives 4 and a water-barrier metallic foil 8 consisting of an aluminum or stainless steel thin film that is bonded on the lower surface thereof by an adhesives 9. A gauge tab of the element 5 is connected with a gauge lead 6 by soldering. The surface of the element 5 and gauge base 3 is covered with a laminate 7. A water-proof resin 13 covers the surface of the strain gauge by means of the laminate 7 and it is bonded or melt-bonded to the peripheral part of the base 3. The foil 8 is stuck on an object 1 to be measured by an adhesives 2. In the strain gauge having such a construction, the foil 8 prevents water content from entering the back side of the base 3 and at the same time the laminate 7 and resin 13 also prevent it from entering the surface side thereof, so the electrical insulation can be kept for a long period.