A thickness meter of tissues (T) of the human body susceptible to be coupled to an applicator for the projection of a beam of ionizing particles on tissues (T) of the body, comprising: a support body (2) having the base (3) susceptible to be arranged as support on the upper surface (S) of the tissues (T) a needle (5) associated with the support body (2) and movable so as to penetrate in the tissues (T) an indicating element (8) movable with the needle (5) with respect to the support body (2) measuring means (10) of the relative movement of the indicating element (8) with respect to the support body (2). The meter (1) has a shape that allows to insert it in the applicator for the projection of a beam of ionizing particles on tissues (T) of the human body so as to allow the measurement of the thickness of such tissues upon the positioning of the applicator.
