To detect sellout by a pressure switch while preventing the discharge of oxidation inhibiting gas sealed together with syrup in a beverage manufacturing apparatus using a syrup storing container consisting of a bag-in-box.

A gas accumulation case 4 having an electrode 19 for detecting gas when syrup storing capacity is more than a cup of beverage and a syrup level is reduced lower than the syrup storing capacity is arranged on the discharge side of a syrup pump 2. When gas is detected by the electrode 10 after discharging the syrup of fixed quantity from the bag-in-box 1 in vending beverage, the syrup pump 2 is driven and the syrup is fed to the case 4 until no gas is detected to always secure the syrup corresponding to a cup of beverage in the case 4. When the pressure switch 8 arranged on the suction side of the syrup pump 2 detects negative pressure before the syrup level in the case 4 reaches a cup of beverage, an alarm of sellout is outputted.