To determine the accuracy of an AD converter more simply than in the related art, a semiconductor device includes a successive approximation AD converter. The AD converter includes one or a plurality of testing capacitors used in a test mode, separately from a C-DAC used for AD conversion in a normal mode. In the test mode, the accuracy of a capacitor under test among a plurality of capacitors configuring the C-DAC is determined by comparing a potential occurring in the capacitor under test and a potential occurring in the testing capacitors.