PROBLEM TO BE SOLVED: To provide an elastic stopper allowing easy needle puncture by reducing puncture resistance in time of the puncture by a puncture needle such as a plastic needle even if the elastic stopper contains a thermoplastic elastomer resin component, and to provide a medical cap including the same.SOLUTION: This elastic stopper 11 for closing an opening of a container includes at least one recessed part 13 for performing the needle puncture of the puncture needle in an optional position of a needle puncture face 14 of the elastic stopper 11, the bottom face of the recessed part 13 is flat, an opening edge part and the bottom face of the recessed part 13 are larger than a maximum diameter of the puncture needle, and the opening edge part of the recessed part 13 has an area not contacting with the puncture needle when performing the needle puncture of the puncture needle into the recessed part 13.
