The present disclosure relates to a signal processing apparatus capable of reducing a circuit scale when transmitting and receiving a signal from an antenna. A first n-type MOS transistor amplifies a transmission signal to be transmitted from the antenna. A second n-type MOS transistor supplies a reception signal to be received from the antenna to a reception circuit. The first n-type MOS transistor and the second n-type MOS transistor are connected to the antenna in series. Furthermore, the reception circuit is connected to a contact between the first n-type MOS transistor and the second n-type MOS transistor. The present disclosure is capable of being applied to, for example, a radio transceiver.