The machine for injecting fluids into meat or fish products comprises an injection head with parallel hollow needles (11) that can be retracted by contrast elastic means, provided to be lifted and lowered in relation to a conveyor for conveying products, each needle (11) having an inlet opening leading into its cannula that can be located in a pressurized fluid injection chamber having a fluid inlet, the chamber being formed by a block with longitudinal ducts interconnected by ducts and a plurality of transverse ducts for the passage of the needles (11) intersecting the longitudinal ducts, each duct comprising sleeves provided with seals, said block being detachable from a housing for the head and fixed by oscillating plates, one for guiding the needles and the other (19) carrying a plurality of cylinders (20) supplying said contrast elastic means.