Abstract: The present invention is a heat-resistant receptacle cap comprising: an inner cap 100 having an insertion pipe 120 configured to be fitted onto an inlet of a receptacle with a locking hook, a discharge gate 140 connected to the insertion pipe 120 with a small-diameter pipe 145 and formed so that contents in the receptacle is discharged at the small-diameter pipe 145, and a container 200 which is installed at the bottom of the small-diameter pipe 145 and has an open upper part to hold additives therein; a heat-resistant sealing plate 220 configured to heat-seal the insertion pipe 120 and upper wall of the container 200; a sealing plate holder 300 which is provided with a fitting ring 310 that fits the sealing plate 220 to a corresponding part for coupling the heat-resistant sealing plate 220, and which is fitted at an upper end of an inner side wall of an outer cap 400; and the outer cap 400 having a sealing plate holder fixing step 420 which is formed on a side wall 401 and configured to separate the seal