In a motor driven bell, a pair of cam members are operatively connected to a drive shaft of a motor. One of the cam members acts directly on a leaf spring for moving a hammer attached to the leaf spring generally in parallel relation to the axis of rotation of the cam member to thereby allow the hammer to strike against an associated gong. The other cam member is disposed generally parallel to the cam member so that the leaf spring interposes therebetween. Therefore, the cam members define an amplitude of the leaf spring, whereby the hammer is able to strike against the gong without mis-striking.