There are provided a fixed terminal device, a control method, and a control program capable of transmitting detection data even when a communication destination is outside a communicable area of a private network. A fixed terminal device 100 is used in a communicable range with both the first and second wireless communication networks different from each other. The fixed terminal device 100 includes a sensor device, first and second reading units 130 and 140, a selection unit 601, and a transmission unit 150. The first and second reading units read authentication information for connecting to the first and second wireless communication networks, respectively. The selection unit selects which of the first wireless communication network and the second wireless communication network to transmit transmission data based on data from the sensor device. The transmission unit, after the wireless communication network selected by the selection unit is authenticated by using the authentication information, transmits the transmission data by using the wireless communication network that has been authenticated.