To provide a detachable connection adaptor that connects, e.g. an earphone terminal to a portable music reproducing device and to provide an electronic device, such as a music reproducing device using the adaptor.

This connection adaptor 500, which connects an earphone 600 to a body 200 of a list type music reproducing device, is provided with an earphone jack 504 and a printed circuit board 505 in continuity with it in a casing 501. A connection terminal 506 made conductive with an earphone connector 205 of main body 200 is penetrated through the casing 501 and made conductive with the printed circuit board 505. Furthermore, the outer face of the causing 501 is provided with a fixed hook 507, meshing with a recessed part 200a of the body 200 and with a moving hook 508, that is turnably integrated and energized with the body 200 and engaged with the recessed part 200b of the body 200.