The present invention relates to a process for preparing a GaAs Hall sensor chip and a GaAs Hall sensor chip, GaAs Hall sensor chip manufacturing method according to an embodiment of the present invention is epitaxially forming a channel layer, the spacer layer and the ohmic layer to the upper GaAs substrate in the order taxi eolcheung forming step; A patterning step to create the epitaxial eolcheung the cross pattern; Electrode forming step of forming the respective electrodes on the epitaxial eolcheung four upper end portions of the cross pattern; Recess etching step to remove all but the ohmic layer on the epitaxial eolcheung inner region where the electrode is not formed; And that after the recess etching step, except for the top surface of the electrode which can reduce the flicker noise of the epitaxial eolcheung are made up formed an insulating film forming step of forming an insulating film covering the GaAs substrate upper GaAs Hall sensor chip It characterized.