A magnetic disk apparatus for high-speed transfer of large amounts of data to a magnetic disk, which uses a redundant disk array system capable of error correction. The housing has a base portion and a lens portion. One of the first optical adhesive and the second optical adhesive is capable of absorbing the light of predetermined wavelength and is adapted to expose the sealant. The working tool is mounted on a stub frame portion pivotal upwardly and downwardly at the front of the frame. 5 and 5\xb0 Cmin to attain a temperature of between 50 and 170\xb0 C, the residence time of said support once the drying temperature is reached being between 20 and 180 min, and calcination of said dried impregnated stabilized oxide support. In the surface of a metal cover which cooperates with a resin base to constitute an adaptor body having a shape corresponding to an outer shape of a large memory card, steps are disposed by partly reducing the material thickness of the cover.