A form-fill-seal machine for filling and hermetically sealing package contents in a tube-shaped packaging material, the form-fill-seal machine comprising: transverse sealing members (54, 74) for transverse-sealing the packaging material in the widthwise direction and forming a bag; gas removal members (56, 76) arranged below the transverse sealing members, the gas removal members coming into contact against the bag prior to sealing of an upper edge by the transverse sealing members, and discharging a gas upwardly from the bag; a movement mechanism for moving the gas removal members (56, 76), switching the position of the gas removal members between at least a first position and a second position with respect to the transverse sealing members; squeezing members (55, 75) arranged below the transverse sealing members, and arranged between the transverse sealing members (54, 74) and the gas removal members (56, 76), the squeezing members coming into contact with the bag prior to transverse sealing by the transverse sealing members, and squeezing the bag downward, characterised in that the form-fill-seal machine further comprises a control mechanism that, in a time slot prior to the start of a transverse sealing action performed by the transverse sealing members (54,74), changes the timing of switching between the first position and the second position, and adjusts the amount of gas discharged from the bag, wherein the control mechanism, at a first switching time, switches the position of the gas removal members (56, 76) from the first position to the second position, increasing the amount of gas discharged from the bag; and, at a second switching time, switches the position of the gas removal members (56, 76) from the second position to the first position, decreasing the amount of gas discharged from the bag, wherein the control mechanism sets the first switching time to precede the second switching time, and sets the second switching time to precede the time at which the transverse sealing action performed by the transverse sealing member commences, the control mechanism being adapted to control the amount of gas discharged from the bag by making adjustments to the duration of the period for which the gas removal members (56, 76) are at the second position. transverse sealing members (54, 74) for transverse-sealing the packaging material in the widthwise direction and forming a bag; gas removal members (56, 76) arranged below the transverse sealing members, the gas removal members coming into contact against the bag prior to sealing of an upper edge by the transverse sealing members, and discharging a gas upwardly from the bag; a movement mechanism for moving the gas removal members (56, 76), switching the position of the gas removal members between at least a first position and a second position with respect to the transverse sealing members; squeezing members (55, 75) arranged below the transverse sealing members, and arranged between the transverse sealing members (54, 74) and the gas removal members (56, 76), the squeezing members coming into contact with the bag prior to transverse sealing by the transverse sealing members, and squeezing the bag downward, characterised in that the form-fill-seal machine further comprises a control mechanism that, in a time slot prior to the start of a transverse sealing action performed by the transverse sealing members (54,74), changes the timing of switching between the first position and the second position, and adjusts the amount of gas discharged from the bag, wherein the control mechanism, at a first switching time, switches the position of the gas removal members (56, 76) from the first position to the second position, increasing the amount of gas discharged from the bag; and, at a second switching time, switches the position of the gas removal members (56, 76) from the second position to the first position, decreasing the amount of gas discharged from the bag, wherein the control mechanism sets the first switching time to precede the second switching time, and sets the second switching time to precede the time at which the transverse sealing action performed by the transverse sealing member commences, the control mechanism being adapted to control the amount of gas discharged from the bag by making adjustments to the duration of the period for which the gas removal members (56, 76) are at the second position.