In a hearing aid, being small in size is one of the most important matters. An ear-hanging and an ear-plugging types of hearing aid are, therefore, comming to be preferred to those for wearing on. A new small sized receiver which is put in such the small hearing aid has been developed. In designing a small sized receiver, the following points are considered as of fundamental conceptions:(a) To be highly sensitive and to be low distortion.(b) To be stable even in any environment.(c) To be of simple construction and easy to manufacture.According to the above conceptions, a new construction of a small size receiver has been proposed. The feature of it consists in the point that the diaphragm including an armature is placed in the gap between the two poles and is directly driven by magnetic force. The target specification of the receiver expected to be 8.5φ6.5 mm in size, and 110 dB (0 dB210-4 µbar/mW, with 2 cc) in sensitivity. In order to make full study and easily on the magnetic and acoustic design of the receiver, the analogical rules have been applied to it, and a triple size model has also been manufactured for trial according those rules. As the result of manufacturing of the actual size receiver, it has satisfied the expected initial specifications with the property of high reliavility and mass productivity at the same time.