A shaft seal packing exhibits high sealability at the time of initial assembly and also exhibits, even after the packing is retightened, excellent sealability by an increased seal surface pressure obtained through an effect of pressing and by self-sealability obtained through an effect of fluid pressure. A shaft seal structure for a valve includes a body for a valve, a valve shaft, a valve disc disposed within the body so as to be rotatable or capable of ascending and descending, a valve shaft seal chamber having the valve shaft axially attached thereto, a shaft seal packing that is attached to the shaft seal chamber and comprises annular packing bodies stacked and substantially V-shaped in cross section, with stacked layer faces on the inner-diameter side of the packing bodies brought into tight contact with one another and stacked layer faces on the outer-diameter side of the packing bodies formed with prescribed gaps between the adjacent stacked layer faces. In the shaft seal structure for a valve, a tightening load on the packing bodies and fluid pressure are converted to a force in the diametrical direction owing to inclined angles of stacked layer faces on the inner-diameter side to attain a seal by a surface contact between the inner peripheral surface on the inner-diameter side and the outer peripheral surface of the valve shaft on a sliding side, and a lip part on the outer-diameter side is pushed and spread owing to the gaps to attain a seal by a line contact with the shaft seal chamber on a fixed side.