The present invention provides a structure of shaft of automatic umbrella, which includes a shaft assembly including a second section having a top end fixed to an internal plug. An inner tube is fixed at a top end thereof to the internal plug and receives therein an operation tube having a bottom coupled to an operation plug. The inner tube receives in a top portion thereof a pulley around which an operation cable wraps. An end of the operation cable is fixed to the bullet-like member and an opposite end fixed to the operation plug. To open the umbrella, a push button is depressed and an expansion spring pushes upward the second section so that the runner cable and the operation cable drive the runner and a third shaft section upward to completely open the umbrella.