A belt type continuously variable transmission includes a continuously variable shift mechanism having a primary pulley, a secondary pulley and a belt wound around the respective pulleys, a pulley thrust calculation unit that calculates a pulley thrust, which is used to bias the respective pulleys in a direction for reducing the pulley width, so as to include a predetermined margin, a hydraulic control unit that controls an oil pressure supplied to each of the pulleys on the basis of the calculated pulley thrust, and an upshift determination unit that determines whether or not an upshift, during which the speed ratio is reduced, is underway. The pulley thrust calculation unit sets the predetermined margin to be smaller when an upshift is determined to be underway than when an upshift is determined not to be underway.