An electrical leakage prevention device in flooding comprising: an input terminal portion including a first input terminal, a second input terminal, and an earth terminal; an output terminal portion including a first output terminal and a second output terminal; a terminal polarity fixing portion disposed between the input terminal portion and the output terminal portion, wherein, in connecting the first and second input terminals (IN1, IN2) to a phase voltage terminal and a neutral point terminal of an electrical outlet for an AC power source, irrespective of cases that (i) the first input terminal and the phase voltage terminal are connected to each other, and at the same time the second input terminal and the neutral point terminal are connected to each other, or (ii) on the contrary the first input terminal and the neutral point terminal are connected to each other, and at the same time the second input terminal and the phase voltage terminal are connected to each other, the terminal polarity fixing portion always makes electrical connections that the first output terminal is connected electrically to the neutral point terminal and at the same time the second output terminal is connected electrically to the phase voltage terminal; a terminal block including a body portion made of insulator and a first connection terminal and a second connection terminal, exposed on the body portion and disposed with an interval to be electrically insulated with each other, and for electrically connecting the first output terminal and the second output terminal to a load respectively; and a leakage-preventing conductor connected electrically to the first connection terminal connected electrically to the neutral point terminal but disconnected electrically to the second connection terminal connected electrically to the phase voltage terminal, and disposed around the second connection terminal so as to enclose at least one of at least a portion of a side of the terminal block, at least a portion of a top of the terminal block, and at least a portion of each of the side and the top of the terminal block respectively, wherein, by the leakage-preventing conductor, when the terminal block is flooded, most of current from the second connection terminal flows through water and into the leakage-preventing conductor and thus any current large enough to cause an electrical shock does not flow through other portions in water, preventing electrical leakage and shock. an input terminal portion including a first input terminal, a second input terminal, and an earth terminal; an output terminal portion including a first output terminal and a second output terminal; a terminal polarity fixing portion disposed between the input terminal portion and the output terminal portion, wherein, in connecting the first and second input terminals (IN1, IN2) to a phase voltage terminal and a neutral point terminal of an electrical outlet for an AC power source, irrespective of cases that (i) the first input terminal and the phase voltage terminal are connected to each other, and at the same time the second input terminal and the neutral point terminal are connected to each other, or (ii) on the contrary the first input terminal and the neutral point terminal are connected to each other, and at the same time the second input terminal and the phase voltage terminal are connected to each other, the terminal polarity fixing portion always makes electrical connections that the first output terminal is connected electrically to the neutral point terminal and at the same time the second output terminal is connected electrically to the phase voltage terminal; a terminal block including a body portion made of insulator and a first connection terminal and a second connection terminal, exposed on the body portion and disposed with an interval to be electrically insulated with each other, and for electrically connecting the first output terminal and the second output terminal to a load respectively; and a leakage-preventing conductor connected electrically to the first connection terminal connected electrically to the neutral point terminal but disconnected electrically to the second connection terminal connected electrically to the phase voltage terminal, and disposed around the second connection terminal so as to enclose at least one of at least a portion of a side of the terminal block, at least a portion of a top of the terminal block, and at least a portion of each of the side and the top of the terminal block respectively,