The present invention discloses an enclosed switchboard (1) in which the inside of a housing (2) is partitioned into a plurality of compartments (a breaker compartment (3), a
bus compartment (4), and a cable compartment (5)). A chamber (8) for alleviating arc-
gas dispersion / pressure
discharge is arranged above the breaker compartment (3), the
bus compartment (4), and the cable compartment (5); and exhaust ducts (9, 10, 11) each of which communicates with the chamber (8) for alleviating arc-
gas dispersion / pressure
discharge are provided in ceiling sections of the breaker compartment (3), the
bus compartment (4), and the cable compartment (5). Flappers (12, 13, 14) are provided in the upper-end sections of the exhaust ducts (9, 10, 11), and a pressure-alleviation shield tank (15) is provided in an opening section (8a) formed in the upper section of the chamber (8) for alleviating arc-
gas dispersion / pressure
discharge. Ventilation sections (12a, 13a, 14a) for providing communication between the exhaust ducts (9, 10, 11) and the chamber (8) for alleviating arc-gas dispersion / pressure discharge are formed on a primary surface of the flappers (12, 13, 14), and mesh members (12b, 13b, 14b) are provided in the ventilation sections (12a, 13a, 14a).