Bundles of well-aligned and randomly-ordered carbon nanotubes were produced by catalytic pyrolysis of a carbon source with quartz glass as a substrate. Their morphologies and pore structures were analyzed by N-2 adsorption at 77 K and by SEM and TEM. According to N2 adsorption, the bundles of aligned carbon nanotubes have a narrow pore distribution mainly in micro- and meso-pores, which is favorable for hydrogen uptake. In hydrogen adsorption measurements at room temperature under moderate pressure (3-10 MPa), we found that the well-aligned carbon nanotube bundles have a hydrogen storage capacity of over 3 wt.%. This suggests that multi-walled carbon nanotubes are a promising material for hydrogen storage.