A multilayer flexible printed circuit board disclosed in the present application is a multilayer flexible printed circuit board in which a ground layer, an insulating layer and a signal wiring layer in which signal wiring is formed are laminated in sequence, with the multilayer flexible printed circuit board including a protruding portion protruding laterally, and a ground that is electrically connected to the ground layer being formed on at least one surface of the protruding portion, in order to have shielding properties that can cope with high speed signal transmission performed via the signal wiring layer.