Electric circuit breaker device

An electric circuit breaker device comprising:

• a housing that encloses an accommodating space extending in one direction as an outer shell member;
• an igniter provided in the housing;
• a projectile that is disposed in the housing, is projected from one end side of the accommodating space by energy received from the igniter, and moves along an extending direction of the accommodating space;
• and
• a conductor piece held by the housing and forming a portion of an electric circuit, the conductor piece including a cutoff portion between a first connection end portion of one side and a second connection end portion on an other side, the cutoff portion being to be cut off by movement of the projectile and disposed crossing the accommodating space, wherein
• a boundary portion with the cutoff portion from which the cutoff portion is cut off in the first connection end portion of the conductor piece held by the housing is defined as a first cutting edge portion, and a boundary portion with the cutoff portion from which the cutoff portion is cut off in the second connection end portion is defined as a second cutting edge portion,
• a groove is formed at a position corresponding to the conductor piece crossing the accommodating space and in a predetermined inter-edge inner wall region positioned between the first cutting edge portion and the second cutting edge portion, in an inner wall surface of the housing, and
• the groove is formed on a path for determining a creepage distance between the first cutting edge portion and the second cutting edge portion in the inter-edge inner wall region.