To provide a cover opening/closing part structure of electric equipment having no possibility of closing a fully opened cover by dead weight since the cover is positioned in a fully opening position even if a lock mechanism or a stopper mechanism is not separately arranged.

A cover 5 is installed in a casing 1 so as to be openable/closable and rockable. A member 2 is positioned in a back part of the cover 5 of a fully opening position. A dimension of a horizontal interval H between a rocking fulcrum P and the member 2 is decided on the length that the cover 5 can rock by falling in the member 2 side with the rocking fulcrum P as the center by the dead weight.