The United States vice president is part of the executive branch. The vice president's only job is to preside over the Senate, and other than that, he takes orders from the president as to what else he should do. If the president needs something done, the vice president will do it, making him part of the executive branch.
Yes, the US vice president is part of the executive branch. The U.S. Constitution is written such that the vice president is available to assist the President and take over if the President is incapacitated. The vice president seldom votes in the Senate, because there are not often ties in modern politics. The vice president is intended to be part of the executive branch and assist the President.