A method and an apparatus for manufacturing medical paper for medical sterilization packaging, medical paper and medical sterilization packaging are disclosed. A paper web is formed of fibrous substrate comprising cellulosic fibres and optionally synthetic fibres, with opposite first and second sides. On-line with the forming of the paper web, reinforcing material is applied on the first side and pressed into structure of the paper web such that delamination resistance of the structure is increased. Sealing material is applied on the second side of the paper web on-line with the forming of the paper web.