A portable data transmitting device, including a storage portion and a movable portion, is disclosed. The storage portion includes a fixed housing including a first side and a second side, and a first plug connector disposed on the first side. The movable portion includes a rotatable housing that is rotatably disposed on the second side of the fixed housing, a slidable housing that includes a first side and is slidably disposed on the rotatable housing, and a second plug connector disposed on the first side of the slidable housing. Thereby, the portable data transmitting device can be attached to portable apparatuses with different thicknesses, and can abut on the portable apparatus so as not to wobble or be bent easily.