A portable storage device which is used by being connected to terminals of an external apparatus, comprises a main body of a rectangular cover case, in which an opening is formed at a front and a fit opening is formed in a wall; a rectangular terminal enclosure supported inside said main body of the cover case, and having a terminal portion at a front for connection with the external terminals, and having a fit portion which is formed in a wall so as to be opposed to said fit opening when inserted into said main body of the cover case; a circuit board which is supported in said terminal enclosure and provided with connector terminals at a front; a semiconductor memory device which is mounted on said circuit board, sealed with resin and connected to said connector terminals; and a fitting member which is inserted into said fit opening of said main body of the cover case so as to be fitted to said fit opening, and to be fitted to said fit portion of said terminal enclosure to thereby fix said main body of the cover case and said terminal enclosure.