The invention relates to a treatment apparatus including a device for conditioning a LASER beam generated by a femtosecond laser, the conditioning device comprising an optical sweeping scanner (30) and a focusing optical system (40) downstream of the optical sweeping scanner (30), remarkable in that a pivoting mirror (32) of the optical sweeping scanner (30) is positioned between an object focal plane Fobject of the focusing optical system (40) and the focusing system (40).