An electromagnetic type acoustic transducer comprises a vibratable diaphragm including a conductor and disposed within a magnetic field defined by a permanent magnet. Support members which are expandable and contractible in the direction at right angles with the diaphragm are fixed to both surfaces of the diaphragm. A frame is provided for fixing the support members such that the expansion and contraction thereof is not prevented. The support members may be folded and formed to a bellows-like state. Use is also made of a conductor forming spiral convolutions. The permanent magnet is disposed and retained at a vibration gap with respect to the diaphragm.