An anti-theft device for a portable device is disclosed, wherein the portable device includes an aperture. The anti-theft device includes a coupler, an engaging/disengaging device, and a localizer. The localizer couples the engaging/disengaging device with an immovable object. The coupler includes a bridge portion and a leg, wherein the bridge portion and the leg are disposed on two different sides of the portable device. The engaging/disengaging device engages with the aperture of the portable device and also couples with the coupler to clamp the portable device.