To provide an internal interruption device which can be subjected to switching test ten times, without transmitting internal explosion to combustible gas or vapor located outside.

A closed motor protective device has a housing formed with a base (10) and a cover (12) received on the base and surrounding a depression (10a) formed in a base. In the cover, a plurality of first wall barriers (122) for closing a first terminal receiving opening and a plurality of second wall barriers (124) for closing a second terminal receiving opening, which have triangular bodies in a sectional view in a longitudinal direction are formed to prevent progression of an arc and ingression of explosive gas into a case. These forms also makes the air supply to the case reduced and weaken the combustion thereby.