A mouse device and a method for assembling and adjusting the same are provided. The mouse device includes an upper housing that includes a button, a middle housing, a bottom housing, a retaining bracket, a sensing switch module, and an adjusting screw. The middle housing is disposed between the upper housing and the bottom housing. The retaining bracket is disposed under the middle housing, and includes a frame and a suspended arm. A fixed end of the suspended arm is fixedly connected to one side of the frame. The sensing switch module is disposed on the suspended arm and corresponds in position to the button. The adjusting screw is disposed at another side of the frame, and is used to adjust a distance between the button and the sensing switch module. The adjusting screw is shielded by the bottom housing and is not exposed from the bottom housing.