A mobile handset having a static preventing device comprises a handset body having components such as a PCB, a detachable battery, a locking member for securing the battery to or for releasing the battery from the handset body, a conductive contact plate located by the locking member, a ground provided at the battery for discharging static electricity, and a switching path from the conductive contact plate to the ground, wherein the switching path is operative when the battery is secured to or released from the handset body.