Provided is a PCB speaker and a method for micromachining the speaker diaphragm on PCB substrate, the method for micromachining the speaker diaphragm on PCB substrate comprises: providing metal paths and at least one through hole on the PCB substrate; providing a patterned sacrificial layer on the PCB substrate, the sacrificial layer covering all the through holes on the PCB substrate; providing a diaphragm layer on the sacrificial layer through depositing, mounting or laminating, the diaphragm layer covering the sacrificial layer and electrically connected with the metal paths on the PCB substrate, thereby forming a diaphragm layer; and releasing the sacrificial layer and the diaphragm layer remains. With the micromachining method for the above PCB substrate and the diaphragm, the production cost of the speaker can be lowered, and the reliability of the product can be improved at the same time.