The present invention discloses a sectional adapter of a clamping holder for automobiles, which can be fixed inside a car by clamping or sticking and has a clamping member for clamping a mobile phone, a PDA, or a palm game. A socket electrically connected to the internal circuit of the adapter is disposed at the rear end of the main body of the clamping holder, so that an adapter can be inserted into the socket to constitute an electrical connection. The adapter is mounted onto the clamping holder by a snap-in member, and a plug of various shapes is disposed at the front edge of the upper section of the adapter for connecting to a corresponding connector of an electronic device.