According to one embodiment, a terminal control substrate includes a base plate mounted on a terminal device, a first module fixed to the base plate, an external connection terminal fixed to the base plate and to which a component including a second module being a substitute for the first module is attachable, a controller configured to perform control in the terminal device by using the first module or the second module, and a switching unit configured to switch a connection destination of the controller to any one of the first module and the external connection terminal to which the second module is attached.