Welding unit for an automatic flexible pouch forming machine comprising: - first and second pressure applicators (11, 21) facing one another, thereby forming a first path for a first pouch precursor made of a folded band of flexible heat-sealable film, - heating means heating at least one of said first and second pressure applicators (11, 21), and - driving means for moving at least one of said first and second pressure applicators (11, 21) between a release position, in which the first and second pressure applicators (11, 21) are separated from the first path, and a welding position, in which the first and second pressure applicators (11, 21) press and apply heat on the first pouch precursor to form a weld, characterized in that it comprises: a first lateral element comprising the first pressure applicator; a central element comprising the second pressure applicator and a third pressure applicator on opposite sides thereof; a second lateral element comprising a fourth pressure applicator facing the third pressure applicator, thereby forming a second path for a second pouch precursor made of a folded band of flexible heat-sealable film; wherein the heating means also heat at least one of said third and fourth pressure applicators (22, 31); and wherein at least one of said third and fourth pressure applicators (22, 31) are movable between a release position, in which the third and fourth pressure applicators (22, 31) are separated from the second path, and a welding position, in which the third and fourth pressure applicators (22, 31) press and apply heat on the second pouch precursor to form a weld; and wherein at least one of the third and fourth pressure applicators (22, 31) is operatively connected to said driving means, so that at least one of said first and second pressure applicators (11, 21) and at least one of said third and fourth pressure applicators (22, 31), simultaneously move from the release position to the welding position, and vice versa. - first and second pressure applicators (11, 21) facing one another, thereby forming a first path for a first pouch precursor made of a folded band of flexible heat-sealable film, - heating means heating at least one of said first and second pressure applicators (11, 21), and - driving means for moving at least one of said first and second pressure applicators (11, 21) between a release position, in which the first and second pressure applicators (11, 21) are separated from the first path, and a welding position, in which the first and second pressure applicators (11, 21) press and apply heat on the first pouch precursor to form a weld, a first lateral element comprising the first pressure applicator; a central element comprising the second pressure applicator and a third pressure applicator on opposite sides thereof; a second lateral element comprising a fourth pressure applicator facing the third pressure applicator, thereby forming a second path for a second pouch precursor made of a folded band of flexible heat-sealable film; wherein the heating means also heat at least one of said third and fourth pressure applicators (22, 31); and wherein at least one of said third and fourth pressure applicators (22, 31) are movable between a release position, in which the third and fourth pressure applicators (22, 31) are separated from the second path, and a welding position, in which the third and fourth pressure applicators (22, 31) press and apply heat on the second pouch precursor to form a weld; and wherein at least one of the third and fourth pressure applicators (22, 31) is operatively connected to said driving means, so that at least one of said first and second pressure applicators (11, 21) and at least one of said third and fourth pressure applicators (22, 31), simultaneously move from the release position to the welding position, and vice versa.