An endoscope valve includes: a piston portion; and an attachment member including a surface forming a hollow space extending in a central axis direction. The piston portion includes: protrusions protruding in a direction perpendicular to the central axis and abutting a surface forming the hollow space of the attachment member; and a seal portion formed in a hollow disk shape with the central axis of the piston portion as a symmetry axis and configured to seal a portion between the attachment member and the seal portion. In the protrusions, when a length of the protrusion in a protrusion direction is indicated by dA, a length of the protrusion in the central axis direction is indicated by dB, and a shrinkage amount of the protrusion when the protrusion comes into pressure-contact with a pressure-contact object is indicated by dC, relationships of dB≤dA and dC