Abstract: The present invention proposes an input device capable of joining modules, which device comprises a keyboard and at least an external module. At least an adapting port and a circuit control unit is attached on a keyboard. Each adapting port is connected to the circuit control unit. At least a joining groove is inwardly formed at each outer edge of the housing of the keyboard. Additionally, the outer edge of each module extends to form a joining plate. Through the join of the joining groove and the joining plate, the keyboard and each module can be joined together. Moreover, the output terminal of each module is connected to one adapting port. Thereby, the functionality of the keyboard can be expanded through linkage with different modules and arbitrary replacement of modules.