Cutter pump comprising a pump body, an impeller mounted on a driving shaft and rotating inside a housing provided in said pump body, a cutting unit mounted coaxially with said impeller and in turn comprising a cutting plate constrained to the pump body and a cutting blade which rotates with respect to said cutting plate, mounted so that it is coaxial with said impeller and rotates together with it, and wherein said cutting blade and said cutting plate cooperate with each other so as to define the cutting interface through which the liquid to be transported is intended to flow, and wherein said cutting blade comprises a through axial opening which is not threaded and is suitable for the insertion of said shaft, and said impeller comprises a through axial opening for the insertion of said shaft, characterized in that said cutting blade and said impeller are mechanically connected to each other and to said shaft by means of a single tab inserted between said shaft and said axial openings (21, 51) of said impeller and of said cutting blade, in such a way that they rotate integrally with each other and with said shaft itself, and wherein one end of said driving shaft projects upstream of the cutting blade, said end being threaded externally so as to allow at least one nut to be screwed thereon, said nut being suited to lock said cutting blade and said impeller onto said shaft, and wherein said cutting plate is mounted between said impeller and said cutting blade and comprises a centre opening at the level of the driving shaft of the impeller, through which said cutting blade and said impeller come into contact with each other, and wherein said cutting blade and said impeller abut against each other thanks to the tightening action of said at least one nut, and wherein said cutting plate is suited to be constrained to said pump body at a selectable distance from said cutting blade, and wherein said pump body comprises at least one fixed portion and at least one adjusting portion to which said cutting plate is rigidly constrained, said adjusting portion being suited to be rigidly constrained to said fixed portion through fixing means, and wherein between said fixed portion and said adjusting portion there are adjustable spacer elements suited to selectively vary the position of said adjusting portion with respect to said fixed portion of the pump body, thus determining also the position of said cutting plate with respect to said cutting blade, and wherein said adjustable spacer elements comprise one or more threaded dowels which are distributed homogeneously and abut against said fixed portion and are engaged in correspondingly threaded seats created in said adjusting portion, and wherein screwing said dowels more or less into said adjusting portion determines the position of said adjusting portion itself with respect to said fixed portion. and wherein one end of said driving shaft projects upstream of the cutting blade, said end being threaded externally so as to allow at least one nut to be screwed thereon, said nut being suited to lock said cutting blade and said impeller onto said shaft, and wherein said cutting plate is mounted between said impeller and said cutting blade and comprises a centre opening at the level of the driving shaft of the impeller, through which said cutting blade and said impeller come into contact with each other, and wherein said cutting blade and said impeller abut against each other thanks to the tightening action of said at least one nut, and wherein said cutting plate is suited to be constrained to said pump body at a selectable distance from said cutting blade, and wherein said pump body comprises at least one fixed portion and at least one adjusting portion to which said cutting plate is rigidly constrained, said adjusting portion being suited to be rigidly constrained to said fixed portion through fixing means, and wherein between said fixed portion and said adjusting portion there are adjustable spacer elements suited to selectively vary the position of said adjusting portion with respect to said fixed portion of the pump body, thus determining also the position of said cutting plate with respect to said cutting blade, and wherein said adjustable spacer elements comprise one or more threaded dowels which are distributed homogeneously and abut against said fixed portion and are engaged in correspondingly threaded seats created in said adjusting portion, and wherein screwing said dowels more or less into said adjusting portion determines the position of said adjusting portion itself with respect to said fixed portion.