A junction box with a square housing and with at least opening and terminal strip for electric cables or lines. With the junction box, a housing arrangement can be modularly built from individual junction boxes that can be reliably connected to one another or to a base part. For attaching the junction box to a second junction box or to a base part, there are two pivotable locking elements on the housing which are movable from a first, open position into a second, locking position, and projecting ribs formed in the area of the outside corners on the housing, the locking element having a U-shape of which a U-bridge is used as an actuating clip and two U-legs, with ends which are bent down, and extend around the ribs on the housing of a second junction box or of the base part in the second, locking position.