Abstract: A valve operated by differential pressure according to the present invention comprises a valve body, a valve disk, a central link, a link, an elastic member, a member attracted by a magnet, and the magnet; the valve disk being mounted on the valve body, the central link being connected at one end to the valve disk, and opening and closing the valve, the link being connected pivotally at one end to the central link, and making the central link move according to rotation of the link around a link pivot, the elastic member being connected pivotally at one end to the link and fixed pivotally at the other end, and making the link rotate around the link pivot by elastic force of the elastic member, the member being mounted on the other end of the central link, the magnet lying adjacent to the member; the valve being closed tightly without leakage of internal fluid until a predetermined differential pressure is reached, then being opened to the maximum stroke thereof as soon as the predetermined differential pressur