To provide a zero adjustment arm used in a positioner capable of effectively preventing harmful effects due to high frequency vibration.

The zero adjustment arm is used in the positioner provided with a pilot valve 21 supplying air to a drive part 51 connected to a valve to drive the drive part, an input part 2 for operating the pilot valve, and a drive control mechanism 41 having a cam 44 connected to the drive part via feedback levers 42 and 43 for giving feedback to driving of the drive part, a range adjustment arm 45 abutting a tip on the cam, a bearing shaft 46 attached to the range adjustment arm, and the zero adjustment arm 47 abutted by the bearing shaft. A portion abutted by the bearing shaft is formed by a material with high hardness.