A multi-functional subminiature speaker, namely a bone conduction speaker, which can generate vibration for a bone conduction function, bodily sensation of vibration, speaker attachment, and the vibration modes over the housing unit, without any projections, and which has an acoustic portion unit detachably mounted. The bone conduction is performed without the projections because the vibration can be generated over the whole surface of the multi-functional subminiature speaker, such that loss of the magnetic force transmitted to the vibration coil is minimized by disposing the magnets on both inner and outer sides with respect to the vibration coil.