To provide a needle cap capable of safely housing a needle part of a syringe needle and preventing the needle part from unexpectedly sticking out after being housed.

A medical needle having a needle tip and a needle base, is fitted into the needle cap from a side. The needle cap includes an inner barrel and an outer barrel. Openings for housing at least part of the needle tip and needle base are formed in the inner barrel and outer barrel. With this structure, by moving the outer barrel of the cap after inserting a syringe needle assembly into the cap, the opening of the inner barrel is closed with the syringe needle assembly in a housed state. The needle does not stick out with a pressure such that the cap or an indwelling needle is not destroyed, even if unexpected pressure is applied in this state.