Abstract: A card reader includes a housing, an interior of which is defined with plural holding slots accommodating interface units respectively. The interface units are connected respectively with control units which are primarily a single chip. The interface units are storage devices, such as MS, CF, SD, XD, USB, microSD or M2. The housing is further provided with a cover board on which are disposed with perforations at locations corresponding to the interface units. When a user is to replace, update or repair the card reader, he or she can take down the cover board and then perform a respective operation to the interface unit to be replaced, updated or repaired independently, without removing other interface units together. Therefore, time and labor works can be reduced, expandability is high, and an unnecessary cost spent can be saved.