This paper proposes a method for the identification ofgeometric deviations in five・ axis machining centers by measurement method based on workpiece coordinate frarne ． The bali bar system is used as a measurement instrument 」 n this method ， one rotary axis and two linear axes are simu ［ taneously controlied and the sensitive direc 重 ion ofthe ba1 匡bar is kept constant in X ， Y or Z direction ofthe machine coordinate accordingl ｝ dn our previous measurement methods ， the sensitive direction of the ball bar is kept constant in radial ， tangential or axial ． The identification of geometric deviations was conducted through s 童 mulation ． From the simulated results ， it is fbund Ihat every deviation can be estimated ． However the identification accuracy ofthe method is less than that ofthe measurement method proposed previously ． Key words ： 5 − axis machining center ， bal レbar method ， 3 − axis control ， geometric deviation 1． 緒 言