An antenna module configured to transmit and receive a radio signal to/from a wireless field device via a wireless network, the antenna module comprising: an antenna configured to transmit and receive the radio signal to/from the wireless field device; a circuit configured to convert a signal received from outside into a radio signal, make the antenna transmit the converted radio signal, and transmit a signal generated by processing the radio signal received by the antenna to the outside; a tubular casing configured to accommodate the circuit to cover a periphery of the circuit; an antenna accommodator ( provided at one end of the casing and configured to accommodate the antenna to allow the antenna to transmit and receive the radio signal; a connector joined to the casing and connectable to an external device configured to transmit and receive a signal to and from the circuit; a router configured to relay the signal processed by the circuit; and a gateway configured to communicatively connect the router and the external device connected to the connector; wherein the circuit comprises: a transmitter-receiver configured to receive the signal from the external device via the connector, output the signal to the gateway, and transmit a signal, which is output from the gateway, to the external device via the connector; and a radio signal processor (24c, F4) configured to convert a signal, which is output from the router, into a radio signal, make the antenna transmit the converted radio signal, and output the signal generated by processing the radio signal received by the antenna to the router, and wherein the gateway is configured to output data, which is output from the transmitter-receiver, to the router, and output data, which is output from the router, to the transmitter-receiver. an antenna configured to transmit and receive the radio signal to/from the wireless field device; a circuit configured to convert a signal received from outside into a radio signal, make the antenna transmit the converted radio signal, and transmit a signal generated by processing the radio signal received by the antenna to the outside; a tubular casing configured to accommodate the circuit to cover a periphery of the circuit; an antenna accommodator ( provided at one end of the casing and configured to accommodate the antenna to allow the antenna to transmit and receive the radio signal; a connector joined to the casing and connectable to an external device configured to transmit and receive a signal to and from the circuit; a router configured to relay the signal processed by the circuit; and a gateway configured to communicatively connect the router and the external device connected to the connector; wherein the circuit comprises: a transmitter-receiver configured to receive the signal from the external device via the connector, output the signal to the gateway, and transmit a signal, which is output from the gateway, to the external device via the connector; and a radio signal processor (24c, F4) configured to convert a signal, which is output from the router, into a radio signal, make the antenna transmit the converted radio signal, and output the signal generated by processing the radio signal received by the antenna to the router, and wherein the gateway is configured to output data, which is output from the transmitter-receiver, to the router, and output data, which is output from the router, to the transmitter-receiver. a transmitter-receiver configured to receive the signal from the external device via the connector, output the signal to the gateway, and transmit a signal, which is output from the gateway, to the external device via the connector; and a radio signal processor (24c, F4) configured to convert a signal, which is output from the router, into a radio signal, make the antenna transmit the converted radio signal, and output the signal generated by processing the radio signal received by the antenna to the router, and wherein the gateway is configured to output data, which is output from the transmitter-receiver, to the router, and output data, which is output from the router, to the transmitter-receiver.