Provided is a twist-cut unsealing mechanism in which an operator can surely sense the fact that twist-cutting of a seal member has completed in assembling of spout and cap of such a type that a container is unsealed by twisting and cutting a seal member for the liquid passage of a spout by means of a cap. A twist-cut unsealing mechanism includes both-side protrusions arranged along a virtual circle rounding around the center line of rotation and an abutment protrusion movable relatively to the both-side protrusions along the virtual circle, and is configured so that one of the both-side protrusion and the abutment protrusion for indicating completion of twist-cut is fixed to a spout (2) and the other protrusion is fixed to a cap (3), the both-side protrusion has a sliding surface of gentle slope and a stopper surface of steep slope wherein projection heights of both surfaces are substantially same in the radial direction and both surface are adjacent to each other along a circle, the abutment protrusion can abut against the sliding surface and the stopper surface, and at a position where the abutment protrusion passed the sliding surface in the rotational direction, the relative rotation positions of the spout (2) and the cap (3) is set above the twist-cut completion position of a seal member (15) and within detachment allowance positional range where the detachment of the cap (3) is permitted.