To ensure high creepage-insulation resistance between a fixed contact and a movable contact and prevent malfunction of a testing circuit caused by pollution by arc gas in current cut-off operation in an electrical leakage testing switch mounted on a mold type zero-phase inverter.

In an earth leakage breaker in which a main circuit contact, a contact opening/closing mechanism, the zero-phase converter, a leakage detecting circuit, a leakage testing switch 12, and others are installed inside a body case of the earth leakage breaker, the fixed contact 12a and the movable contact 12b of a leakage testing switch 12 are mounted on the zero-phase converter 9 which becomes a resin mold shape, a mold case 9a of the zero-phase converter is covered with spongy foamed resin sheet 17 so as to surround the fixed contact of the testing switch, and high creepage-insulation resistance is ensured between the fixed contact and the closed contact of the testing switch. The foamed resin sheet 17 is formed with a silicone resin foam in which a square hole 17a is opened in the center of the sheet surface, the square hole is positioned to the fixed contact of the testing switch, and stuck to the fixed contact of the testing switch with an adhesive.