The invention discloses a surface roughness measuring instrument with an adjustment limiting function. The instrument comprises a supporting seat, a supporting table arranged at the top of the supporting seat, a feeding mechanism, a receiving trolley, a clamping mechanism, a supporting column, a supporting plate, a lifting rod, a moving plate and a measuring mechanism, the supporting column and the supporting plate are fixedly arranged at the two ends of the top of the supporting table respectively, the lifting rod is arranged between the supporting column and the supporting plate, the liftingrod is slidably connected between the supporting column and the supporting plate, the moving plate is slidably connected to the surface of the lifting rod, the measuring mechanism is arranged at thebottom of the moving plate, and sliding rods are symmetrically arranged on the surface of the lifting rod. According to the surface roughness measuring instrument, the height and the horizontal position of the surface roughness measuring instrument can be adjusted, the surface roughness measuring instrument can be rotated to a certain degree through the arrangement of a gear motor, a mounting plate and an arc-shaped groove, a workpiece with the surface at a certain gradient can be measured conveniently, and the measuring range is wide.