This invention relates to a belt driven continuously variable transmission having a pressure regulating cam mechanism giving an axial force corresponding to the transmission torque to a pulley and preventing too much belt pressing force. A retainer is fixed on a boss section of a stationary sheave and a spring made of multiple disc springs is situated on the outer surface of a boss section of a movable sheave for contact the retainer. A spring apparatus is composed of the retainer and the spring. Accordingly, at the decelerating range with large shifting ratio, besides the axial force made by the pressure regulating cam mechanism, the spring apparatus generates pressing force by contacting the retainer and maintains the belt holding force. When the shifting ratio is small, the spring returns to its natural length and disengages from the retainer.