Abstract: A bone conduction speaker having a vibration prevention structure is disclosed. In the speaker structure that a magnet and a voice coil are installed in the interior of a housing disposed in an inner side of an external casing of a bone conduction speaker and are engaged with a yoke, and a diaphragm is installed in an outer side of the yoke, there is provided a bone conduction speaker having a vibration prevention structure which comprises one or at least two ribs which are formed as an outer side of the diaphragm is outwardly extended; and an engaging part which is disposed in an end of each rib and is fixedly assembled to the casing.