This watch case comprises a protective casing surrounded by a middle (5) and a bezel (9). The protective casing includes a glass (3), a side wall (2) and a bottom (1). A planar peripheral surface extending along the entire edge of the inner face of the glass is in contact with a similar bearing surface on the side wall (2), at least part of which forms the width of the cross section of a pressure resistant structure having parallel lateral faces (SR) perpendicular to the bearing surface, and which extends without a gap as far as the bottom (1) of the casing. The components of the casing are secured and sealed with at least one annular seal (4) surrounding the lateral face of the glass (3) and the outer lateral face of the side wall (2) of the casing, and this seal is clamped.