The present application relates to an unfolding device of sofa, including a base. A side plate is provided above the base, and a connecting rod assembly is connected between the side plate and the base; the side plate is provided with a mounting assembly for connecting to a sitting portion; a footrest assembly and a backrest connecting member is mounted on and rotatably connected with the side plate; the base is provided with a driving assembly, configured for driving the footrest assembly to rotate and the side plate to move towards a front of the unfolding device.