In a speed ratio control device for a belt continuously variable transmission according to this invention, when a speed ratio is subjected to feedback control on the basis of a difference between an actual speed ratio and a target speed ratio, pressure supplied to a primary pulley is corrected through feedforward (S17, S18) in order to suppress variation in the groove width of the primary pulley caused by a rapid variation in an input torque into the primary pulley (S17) while traveling in a fixed speed ratio mode (S14) in which the target speed ratio is held at a fixed value.