In a semiconductor strain detector, the temperature characteristic of the output of a zero-point temperature compensating circuit is added to the zero-point temperature characteristic of the output of a bridge circuit composed of strain gauges, to perform a zero-point temperature compensation of the final output. Further, two kinds of diffusion resistors having different surface impurity densities are used in each amplifying circuit to perform a sensitivity-temperature compensation in which a temperature coefficient of sensitivity is considered up to the second-order term.