An oscillating descaler (1) for semi-finished metallurgical products comprises:—a passageway (2) delimited by two opposite input and output sections (3, 4) crossable by a semi-finished product (10) to be descaled according to a rectilinear crossing direction (X) oriented from the input section (3) to the output section (4),—a manifold (20) for a pressurized fluid extended according to a longitudinal direction (Y) defined between first and second longitudinally opposite ends (21, 22), arranged so that the longitudinal direction (Y) is not parallel to the crossing direction (X),—at least one nozzle (30) for spraying a jet (31) according to a spray direction (Z) which is coaxial to a hole (30a) of the nozzle (30) and inclined towards the input section (3) and towards one of the ends (21, 22) of the manifold (20, 20b),—motor means (M) for generating a rectilinear oscillating motion of the jet (31) along the longitudinal direction (Y).