A mowing head for a trimmer is rotated about an axis of rotation when operated and has a housing with a circumferential wall. A fastening device with a trimmer line guide with a trimmer line channel is provided for the trimmer line. The trimmer line channel has a clamping section with a longitudinal direction. The clamping section has a wide longitudinal side and a narrow longitudinal side, both extending in the longitudinal direction. The clamping section has an inner width tapering from the wide longitudinal side toward the narrow longitudinal side. The trimmer line guide has a deflection edge adjoining the clamping section. The deflection edge is slanted relative to the longitudinal direction such that the deflection edge generates a force component acting on the trimmer line directed toward the narrow longitudinal side when a pulling force is acting on the trimmer line guided through the fastening device.
