Device for containing fluid substance, including a bag having at least one flexible side wall, a substantially rigid neck delimiting an opening giving access to an internal cavity of the bag, shaped to at least partially accommodate a pumping member for pumping the fluid substance, and provided with a connector for connection to an external container. The bag is made from multilayer material, and the neck is made from a material different from bag material and includes a cup-shaped element having a bottom wall with at least one opening, and a side wall on the outer surface of which the upper edge of the bag is hermetically connected. The device includes a valve element for moving from an opening position, wherein the valve element makes the bag internal cavity accessible, and a closing position, wherein the valve element inhibits access to the internal cavity.