A speaker diaphragm 1 includes a first diaphragm portion 5, a second diaphragm portion 6 integrally molded with the first diaphragm portion 5, and a bobbin-receiving portion 7 protruding from a back side of a connecting portion between the first diaphragm portion 5 and the second diaphragm portion 6, with one end of a voice coil bobbin 2 being bonded to the bobbin-receiving portion 7. The bobbin-receiving portion 7 includes a first extension 8 extending backwards from the first diaphragm portion 5 and a second extension 9 extending backwards from the second diaphragm portion 6. A bobbin-receiving groove 10 is defined between the first extension 8 and the second extension 9. The voice coil bobbin 2 is inserted in and bonded to the bobbin-receiving groove 10.