The present disclosure provides a lower electrode mechanism and a reaction chamber, the lower electrode mechanism includes a base for carrying a workpiece to be processed and a lower electrode chamber disposed under the base, the lower electrode chamber includes an electromagnetic shielding space and a non-electromagnetic shielding space isolated from each other, the chamber of the lower electrode chamber includes a first through hole and a second through hole, and the electromagnetic shielding space and the non-electromagnetic shielding space are respectively connected to outside through the first through hole and the second through hole to prevent a plurality of first components disposed in the electromagnetic shielding space from being interfered by a second component disposed in the non-electromagnetic shielding space.