A systematic examination of the cryogenic H2 adsorption properties below critical point of H2 (Tc = 33 K) on a various kind of adsorbents was carried out, then the density of adsorbed H2 on each adsorbent and its temperature dependence were experimentally compared with the liquid H2. Usually, H2 adsorption on porous materials was investigated at liquid nitrogen temperature (77 K) to realize its practical application for H2 storage and most of reports have focused on the development of new porous materials. On the other hand, this work was focused for the first time on the cryogenic H2 adsorption properties of metal organic frame works, superactivated carbon, and graphene nanoplatelets. We found superdense H2 adsorption as the monolayer state, having much higher density than liquid H2, which is contrary to the general understanding that the upper limit of adsorbed H2 density is believed to the density of liquid H2.