A leakage current detection and interruption (LCDI) device includes a switch module to control electrical connection of first and second power supply lines between input and output ends, a leakage current detection module including first and second leakage current detection lines respectively covering the first and second power supply lines to detect leakage currents thereon, a detection monitoring module coupled to the leakage current detection module and the first and second power supply lines to generate an open circuit detection signal in response to an open circuit condition in the first or second leakage current detection line, and a test module including a normally closed test switch coupled to the first or second leakage current detection line, wherein when the test switch is manually operated to open, the switch module disconnects the first and second power supply lines between the input and output ends.