An inflatable belt device includes a tongue having a rear end connected to an inflatable belt; a buckle with which the tongue is to be engaged; and a gas generator or inflator for supplying gas into the buckle. The tongue includes a tongue base having a gas passage or duct; a tongue plate fixed to the tongue base; and a lap belt anchor. The lap belt anchor has an L-like configuration and includes a base and a bracket, which extends perpendicularly from the base and has an opening formed therein. The base is attached pivotally to the tongue plate by a pivot pin. A sheet, made from a low friction material, may be placed between the plate and the base, thus facilitating the pivoting of the tongue. As a result of this arrangement, gas is introduced much more smoothly from a tongue of an inflatable belt device into the inflatable belt. A low pressure gas generator may thus be used.