Disclosed is an inner cap. The inner cap comprise a cap body part engaged with the inlet of a container through a pressing force applied in the engagement direction; and a support part which is arranged on the cap body part and which prevents the cap body part from being deformed by the pressing force by supporting the cap body part against the pressing force. The present invention prevents the inner cap from being deformed and falling into the container while the inner cap is attached to the inlet of the container to seal the container as the deformation of the inner cap caused by the pressing force is prevented by the support part.
