Expansion device

An expansion device suitable for expanding capabilities of a mobile device, comprising:

• at least one mobile device;
• an input/output body, having a first input/output module and a second input/output module disposed respectively on two opposite surfaces of the input/output body;
• a connection part, disposed on one side of the input/output body;
• a turning structure, disposed to connect the input/output body and the connection part, wherein the connection part and the input/output body are turnable on the turning structure;
• and
• at least one slot, disposed on the connection part and configured to hold the at least one mobile device,
• wherein a recess is disposed onto the side of the input/output body on which the connection part is disposed, the connection part is capable of being turned into the recess, and the connection part is capable of being turned to enable an end surface of the connection part reaches a position against an end surface of the recess, and
• wherein the at least one mobile device, after being held by the slot and turned no more than 180 degrees, is perpendicular to the input/output body.