A sample transfer mechanism comprising: a plurality of openable gripping arms that are configured to grip a body portion of a sample vessel (710, 711, 800), the sample vessel (710, 711, 800) having an opening portion, a bottom portion, and the body portion being available in a plurality of types having different lengths and shapes (710, 711, 800); and an elevating mechanism that is configured to lower the gripping arms to a predetermined position relative to a sample vessel (710, 711, 800) to be gripped, characterized in that: the sample transfer mechanism includes a control mechanism that is configured to control a lowering distance of the elevating mechanism such that a gripping position at which the gripping arms grip the sample vessel (710, 711, 800) having different lengths (730, 731) is identical among the plurality of types of sample vessels (710, 711, 800) by positioning the gripping arms at a predetermined distance from an upper surface of a holder to hold the sample vessel (710, 711, 800), wherein a drive pattern is stored in a drive pattern storage unit of the control mechanism, the gripping position is an area on an outer surface of the sample vessel (710, 711, 800) body portion, the sample transfer mechanism includes a cover that covers an outside of leading end portions of the gripping arms and has a lower end disposed downwardly of the leading end portions of the gripping arms, and the cover has grooves formed in the inner wall thereof, the grooves corresponding in number with the gripping arms for housing therein the gripping arms, wherein when the gripping arms are fully open, each of the gripping arms is perpendicular to an upper end surface of the holder, and when the gripping arms are open, all gripping arms have at least the leading end portions resting inside the grooves. a plurality of openable gripping arms that are configured to grip a body portion of a sample vessel (710, 711, 800), the sample vessel (710, 711, 800) having an opening portion, a bottom portion, and the body portion being available in a plurality of types having different lengths and shapes (710, 711, 800); and an elevating mechanism that is configured to lower the gripping arms to a predetermined position relative to a sample vessel (710, 711, 800) to be gripped, characterized in that: the sample transfer mechanism includes a control mechanism that is configured to control a lowering distance of the elevating mechanism such that a gripping position at which the gripping arms grip the sample vessel (710, 711, 800) having different lengths (730, 731) is identical among the plurality of types of sample vessels (710, 711, 800) by positioning the gripping arms at a predetermined distance from an upper surface of a holder to hold the sample vessel (710, 711, 800), wherein a drive pattern is stored in a drive pattern storage unit of the control mechanism, the gripping position is an area on an outer surface of the sample vessel (710, 711, 800) body portion, the sample transfer mechanism includes a cover that covers an outside of leading end portions of the gripping arms and has a lower end disposed downwardly of the leading end portions of the gripping arms, and the cover has grooves formed in the inner wall thereof, the grooves corresponding in number with the gripping arms for housing therein the gripping arms, wherein the sample transfer mechanism includes a control mechanism that is configured to control a lowering distance of the elevating mechanism such that a gripping position at which the gripping arms grip the sample vessel (710, 711, 800) having different lengths (730, 731) is identical among the plurality of types of sample vessels (710, 711, 800) by positioning the gripping arms at a predetermined distance from an upper surface of a holder to hold the sample vessel (710, 711, 800), wherein a drive pattern is stored in a drive pattern storage unit of the control mechanism, the gripping position is an area on an outer surface of the sample vessel (710, 711, 800) body portion, the sample transfer mechanism includes a cover that covers an outside of leading end portions of the gripping arms and has a lower end disposed downwardly of the leading end portions of the gripping arms, and the cover has grooves formed in the inner wall thereof, the grooves corresponding in number with the gripping arms for housing therein the gripping arms, wherein when the gripping arms are fully open, each of the gripping arms is perpendicular to an upper end surface of the holder, and when the gripping arms are open, all gripping arms have at least the leading end portions resting inside the grooves.