A machine for making filter bags for infusion products starting from pieces of filter material each having two free ends ( 1d, 1e) and an intermediate portion, between each free end ( 1d and 1e) and the intermediate portion having, respectively, two chambers ( 1b, 1c) containing a corresponding dose of product; the pieces advancing along a feed line of the machine, comprising: - a first carousel for continuous rotary movement about a first axis of rotation and having at least a plurality of first operating stations positioned along, and continuously movable with, the first movement carousel, each first operating station being configured to retain and operate on a corresponding piece of filter material fed along at least one predetermined angular stretch of rotation of the first movement carousel, to obtain at least a lifting of the two chambers ( 1b, 1c) to a position side by side and erect, that is to say, positioned radially relative to the first axis of rotation; characterised by further comprising: - a second movement carousel positioned alongside the first carousel and rotating continuously about a second axis of rotation parallel to the first axis of rotation; the second carousel having a plurality of joining elements positioned along, and continuously movable with, the second carousel; each joining element being connected to corresponding control devices ( 8, 9) configured for actuating, in a synchronised fashion with the corresponding rotations of the first and the second carousel and at least along a stretch of predetermined curved path, a succession of movements of the joining element to intercept the free ends ( 1d, 1e) of the piece of erected filter material, positioned on the operating station and joining them, towards one of the two chambers ( 1b, 1c) containing a dose of product. - a first carousel for continuous rotary movement about a first axis of rotation and having at least a plurality of first operating stations positioned along, and continuously movable with, the first movement carousel, each first operating station being configured to retain and operate on a corresponding piece of filter material fed along at least one predetermined angular stretch of rotation of the first movement carousel, to obtain at least a lifting of the two chambers ( 1b, 1c) to a position side by side and erect, that is to say, positioned radially relative to the first axis of rotation; characterised by further comprising: - a second movement carousel positioned alongside the first carousel and rotating continuously about a second axis of rotation parallel to the first axis of rotation; the second carousel having a plurality of joining elements positioned along, and continuously movable with, the second carousel; each joining element being connected to corresponding control devices ( 8, 9) configured for actuating, in a synchronised fashion with the corresponding rotations of the first and the second carousel and at least along a stretch of predetermined curved path, a succession of movements of the joining element to intercept the free ends ( 1d, 1e) of the piece of erected filter material, positioned on the operating station and joining them, towards one of the two chambers ( 1b, 1c) containing a dose of product. - a second movement carousel positioned alongside the first carousel and rotating continuously about a second axis of rotation parallel to the first axis of rotation; the second carousel having a plurality of joining elements positioned along, and continuously movable with, the second carousel; each joining element being connected to corresponding control devices ( 8, 9) configured for actuating, in a synchronised fashion with the corresponding rotations of the first and the second carousel and at least along a stretch of predetermined curved path, a succession of movements of the joining element to intercept the free ends ( 1d, 1e) of the piece of erected filter material, positioned on the operating station and joining them, towards one of the two chambers ( 1b, 1c) containing a dose of product.