In an exemplary embodiment, a connection device includes a cable unit, first and second connector units, and a circuit board. The first connector unit is provided at a first end of the cable unit and is connectable to a host device. The second connector unit is provided at a second end of the cable unit and is connectable to a terminal device. The circuit board includes a control unit and is provided in one of the first and second connector units. The control unit includes a storage unit and a management unit. The storage unit stores operation data indicating operation content of the connection device. The management unit manages the operation data, and changes the operation data on the basis of instruction data received from the host device if the connection device is connected to the host device and the terminal device.