A semiconductor device is disclosed. The semiconductor device includes an internal circuit having a high breakdown voltage transistor, and a first electrostatic protection circuit in which electrostatic protection elements are connected in series. The sum of the breakdown voltage values of the electrostatic protection elements in the first electrostatic protection circuit is almost equal to the breakdown voltage value of the high breakdown voltage transistor. The first electrostatic protection circuit is connected between an input/output terminal and a ground terminal of the semiconductor device to which terminals the internal circuit is connected.