The invention provides a treatment device (100) for fractional laser-based skin treatment. The treatment device comprises an emission window (70) comprising an elongated area (75) and a plurality of predefined locations (74) in said elongated area (75), wherein the predefined locations (74) are arranged in an elongated array which extends along a treatment axis (72) of the window (70), and wherein each predefined location (74) in the array is located at a distance from the treatment axis (72), seen in a direction perpendicular to the treatment axis (72), which is smaller than 25% of a maximum distance between two predefined locations (74) in the array, seen in a direction parallel to the treatment axis (72). The treatment device further comprises a treatment generator (80) comprising a treatment laser (20) for emitting laser light (21) towards skin tissue (110) from said plurality of predefined locations (74) in the emission window (70) for generating, in use, laser-based lesions (120) inside the skin tissue (110). The treatment device further comprises a motion sensor (90) for sensing motion of the treatment device relative to the skin surface (105) and a controller (60) for determining a non-zero sequence of at least one of the plurality of predefined locations in the emission window from which laser light is consecutively emitted in dependence on the sensed motion. The controller is configured to activate the treatment generator to generate said non-zero sequence when the sensed motion of the treatment device relative to the skin surface only has a component in a direction parallel to the treatment axis.
