The grass-cutting head (1) with cutting line (F) includes an outer housing (3) and a spool (5) housed in the outer housing. The spool includes an axial cavity (9) and two opposite channels (17) for insertion of the cutting line (F). A spring (11), elastically biases the spool with respect to the housing, and two bushings (7) are approximately diametrically opposite in a lateral wall of the outer housing (3), which are alignable with openings of the two opposite cutting line insertion channels. In the axial cavity (9) of the spool (5) there are formed two opposite projections (21) for supporting the spring (11), forming pairs of lead-in and guide surfaces (21A) converging toward respective openings (17B) of the two opposite cutting line insertion channels, facing the axial cavity (9) of the spool (5).
