A network telephone expansion seat including a housing and a signal conversion module is provided. The housing has a bearing portion for disposing a network telephone thereon. The signal conversion module disposed inside the housing has a circuit substrate. At least one connection interface for transmitting data is disposed on the circuit substrate for connecting the network telephone to transmit data. Meanwhile, the circuit substrate is connected to peripherals such as a printer, a facsimile machine, a card reader, and an MP3 player via the connection interface, thereby expanding the functions of the network telephone.