The present invention concerns a fluid purifying device (10) purifying a fluid comprising an inlet opening (36) of the fluid and an emission opening (42) of the fluid. The device (10) further comprises: - an outer tube (16) having a first end positioned on the first side (L1) of the device (10) relative to a reference plane (R), the inlet opening (36) of the fluid being defined at said first end (26) of the outer tube (16), - an inner tube (20), arranged within the outer tube (16) and having a second end (31 ) positioned on a second side (L2) of the device (10), opposite to said first side (L1) relative to the reference plane (R), the emission opening (42) for the fluid being defined at said second end (31) of the inner tube (20); - an intermediate tube (18), arranged between the outer tube (16) and the inner tube (20) so as to define a mandatory and continuous fluid path (P) between the inlet opening (36) and the emission opening (42), said path (P) including a first stretch (P1)) confined between the outer tube (16) and the intermediate tube (18), a second stretch (P2) confined between the intermediate tube (18) and the inner tube (20) and a third stretch (P3) confined within the inner tube (20); and - a UV-C radiation source arranged within the outer tube (16) so as to irradiate the fluid at least along the first stretch (P1) of the fluid path (P).