Method for washing a plastics material and for separating contaminating substances therefrom, comprising the steps of: a. supplying a first flow (F IN) of a washing fluid together with the plastics material containing the contaminants in a washing container in which stirrer means is in movement to generate a turbulent stirring action intended to detach from the plastics material, through mechanical action, the part of contaminating material adhering thereto, enabling a first fraction of heavier contaminants to precipitate onto a first bottom portion of said washing container, thus performing a first action of separating contaminants, b. transferring by overflow a second flow (F 2) of washing fluid with floating plastics material from the washing container to a first chamber of a separating tank (V S), in which a second separating action occurs with the precipitation of a second fraction of contaminants to a second bottom portion of said first chamber, c. conveying a third flow (F 3) of washing fluid with floating plastics material from said first chamber to a second chamber of said separating tank (V S) and evacuating by overflow an outgoing flow (Fout) of washing fluid together with the processed plastics material (P'), in which in the transit from said first chamber to said second chamber there is provided d. disaggregating the floating agglomerates of plastics material and imparting to said third flow (F 3) and to the plastics material a downward propelling action inside said second chamber to promote a third separating action with precipitation of a third fraction of contaminants onto a third bottom portion of said second chamber, e. removing, from below said separating tank (V S), a recirculation flow (F R) comprising washing fluid and precipitated contaminants and sending said recirculation flow (F R) to a separating screen unit (U S) to retain said contaminants and return the washing fluid to said separating tank (Vs). a. supplying a first flow (F IN) of a washing fluid together with the plastics material containing the contaminants in a washing container in which stirrer means is in movement to generate a turbulent stirring action intended to detach from the plastics material, through mechanical action, the part of contaminating material adhering thereto, enabling a first fraction of heavier contaminants to precipitate onto a first bottom portion of said washing container, thus performing a first action of separating contaminants, b. transferring by overflow a second flow (F 2) of washing fluid with floating plastics material from the washing container to a first chamber of a separating tank (V S), in which a second separating action occurs with the precipitation of a second fraction of contaminants to a second bottom portion of said first chamber, c. conveying a third flow (F 3) of washing fluid with floating plastics material from said first chamber to a second chamber of said separating tank (V S) and evacuating by overflow an outgoing flow (Fout) of washing fluid together with the processed plastics material (P'), in which in the transit from said first chamber to said second chamber there is provided d. disaggregating the floating agglomerates of plastics material and imparting to said third flow (F 3) and to the plastics material a downward propelling action inside said second chamber to promote a third separating action with precipitation of a third fraction of contaminants onto a third bottom portion of said second chamber, e. removing, from below said separating tank (V S), a recirculation flow (F R) comprising washing fluid and precipitated contaminants and sending said recirculation flow (F R) to a separating screen unit (U S) to retain said contaminants and return the washing fluid to said separating tank (Vs).