A SPA machine includes a housing provided with a water sprayer, a water pump mounted in the housing for pumping water out of the water sprayer, and a pressure-balancing watertight electric control device formed of a box, watertight buttons, an electric control unit, a watertight panel and a locating frame and mounted the housing for controlling the operation of the water pump and having a variable inside space automatically regulated subject to the external water pressure to prevent water penetration and to avoid electric leakage.