Abstract: A cap for a bottle, having a top wall provided with an annular projected part, a skirt portion suspending downward from the peripheral edge of the top wall, a tab suspending downward from a part of the lower edge of the skirt portion, a pair of first separating lines extending toward the top wall from the vicinity of the intersection of the peripheral edge of the tap and the lower edge of the skirt portion, and a pair of second separating lines extending to the vicinity of the upper end of the skirt portion from the lower edge thereof, wherein the distance between the upper ends of the first separating lines is designed such that the terminal ends of the tearing of the first separating lines themselves, or of the tearing effected beyond the lines, are positioned on the tangent line of the internal peripheral circle of the annular projected part.