The invention relates to a low load swinging mechanism for a sander. The sander includes a roller unit that has a positioning base provided with two sliding rails for contacting with a connecting member of a sliding base. The sliding rail has an arc surface and the connecting member possesses a corner groove recessed with a certain angle, so that the surface of the corner groove is to contact linearly with the arc surface of the sliding rail to reduce a great abrasion resistance as the sliding base is reciprocating on the positioning base, for upgrading grinding precision.
