Portable device for remotely operating a device in a vehicle

A portable device for facilitating adjustment of the area in which communication with a controller is enabled. The portable device performs wireless communication with an in-vehicle device, which controls a door lock driver or an engine starter of a vehicle, to remotely control the in-vehicle device.. The portable device includes a receiver for receiving a request signal from the in-vehicle device and a control unit for lowering or raising the signal receiving sensitivity of the receiver by predetermined levels to adjust the signal receiving sensitivity.