A loudspeaker diaphragm having light weight and an excellent balance between a rigidity and an internal loss, and a simple and inexpensive method for manufacturing such a diaphragm are provided. The loudspeaker diaphragm includes a base layer having a woven fabric of a polyethylene naphthalate fiber impregnated with a thermosetting resin, and optionally a thermoplastic resin layer and/or a thermoplastic elastomer layer. The polyethylene naphthalate fiber is preferably an untwisted fiber. A fiber/resin weight ratio in the base layer is preferably in the range of 60/40 to 80/20. Preferably, the thermoplastic resin layer has a finely foamed structure and an average diameter of a cell in the finely foamed structure is 10 to 60 .mu.m.