Abstract: This invention relates to a scroll bar input device for a mouse, the scroll bar input device being installed inside mouse body for executing a scroll up or scroll down action for the computer screen. The scroll bar input device has a base, a locating seat, a first shaft bracket, a roller, a rotating wheel, an encoder, a second shaft bracket and a microswitch. The first shaft bracket has a wheel hub with contacts, the wheel hub inserted into the rotating wheel. The encoder is in contact with first teeth of the rotating wheel to transmit or receive signals for moving up and down the computer screen.