In a semiconductor device, a sine wave signal is input to a first input part and a cosine wave signal is input to a second input part. A multiplexer alternately selects one of the sine wave signal and the cosine wave signal. An analog to digital converter converts the output signal of the multiplexer into a digital value. A switching circuit is coupled between at least one of the first and second input parts and the multiplexer. The switching circuit is configured to be able to invert the input sine wave signal or the input cosine wave signal, in order to reduce the angle detection error due to the non-linearity error of the A/D converter.