A machine for forming filter-bags containing infusion products of the type comprising a piece of filter material with an elongate shape having at least two chambers (2, 3) containing corresponding doses (D1, D2) of infusion product; the machine comprising: - a folding station designed to fold the piece of filter material and positioned along a line for feeding and forming; - a receiving carousel designed to receive from the folding station and move the piece of filter material to at least one operating station designed to make a filter-bag starting from the piece of filter material; the folding station, comprising: - two receiving surfaces (5, 6) designed to receive the piece of filter material and having surfaces mutually converging to define a channel facing towards the receiving carousel; - a pair of gripping elements (9, 10) operatively positioned on opposite sides of the channel; - movement means designed to move with a synchronised reciprocal movement the gripping elements (9, 10) towards, and away from, the receiving carousel; the pair of gripping elements (9, 10) acting on both sides at an intermediate zone of the piece of filter material for folding, and transferring to the underlying receiving carousel, the piece of filter material, characterised in that the folding station comprises: - two flat auxiliary walls (12, 13), one for each receiving surface (5, 6), movable between an operating position for receiving, wherein the flat auxiliary walls (12, 13) receive the piece of filter material advancing along a feed line and are mutually coplanar, and an operating position for controlled release, wherein the flat auxiliary walls (12, 13) are inclined towards the channel defined by the receiving surfaces (5, 6) and are designed to release in a controlled manner the piece of filter material to the underlying receiving carousel; - movement devices, synchronised with the movement means, designed to move the flat auxiliary walls (12, 13) from the operating position for receiving to the operating position for controlled release and vice versa. - a folding station designed to fold the piece of filter material and positioned along a line for feeding and forming; - a receiving carousel designed to receive from the folding station and move the piece of filter material to at least one operating station designed to make a filter-bag starting from the piece of filter material; the folding station, comprising: - two receiving surfaces (5, 6) designed to receive the piece of filter material and having surfaces mutually converging to define a channel facing towards the receiving carousel; - a pair of gripping elements (9, 10) operatively positioned on opposite sides of the channel; - movement means designed to move with a synchronised reciprocal movement the gripping elements (9, 10) towards, and away from, the receiving carousel; - two flat auxiliary walls (12, 13), one for each receiving surface (5, 6), movable between an operating position for receiving, wherein the flat auxiliary walls (12, 13) receive the piece of filter material advancing along a feed line and are mutually coplanar, and an operating position for controlled release, wherein the flat auxiliary walls (12, 13) are inclined towards the channel defined by the receiving surfaces (5, 6) and are designed to release in a controlled manner the piece of filter material to the underlying receiving carousel; - movement devices, synchronised with the movement means, designed to move the flat auxiliary walls (12, 13) from the operating position for receiving to the operating position for controlled release and vice versa.