A machine for injecting brine into meat pieces includes a conveyor having a support surface for conveying meat pieces in a forward step by step movement, each step having a predetermined length, first and second injection heads consecutively arranged over the conveyor relative to the forward direction, each injection head having an array of injection needles covering a whole width of the conveyor support surface. A length of the conveyor support surface corresponds to the predetermined length of the steps of the conveyor step by step movement, head driving device for alternately reciprocating the injection heads between an upper position, enabling the meat pieces to pass under the injection heads, and a lower position, where the injection needles are stuck into the meat pieces located under the injection heads, and brine supplying device supplying brine to the injection needles at least when the injection heads are at their lower position.