It is an object to reduce defects caused by reading wrong data by judging whether a storage state held in a non-volatile memory element is correct or not in the case where accumulation or discharge of electrons in/from a charge accumulation layer. A semiconductor memory circuit including a memory cell region and a test region and a control circuit are included in a semiconductor device of the present invention. In the control circuit, a first operation is performed for writing data to a memory cell, and writing a first storage state to a first region or writing a second storage state to a second region. Then, a second operation is performed for reading a first storage state or a second storage state from a first region and a second region. Further, a third operation is performed for reading data from the memory cell. Whether the third operation is correctly performed or not is judged in accordance with whether the first storage state is read from the first region or not or whether the second storage state is read from the second region or not in the second operation.