A direction shifting mechanism for changing a direction of a sample tube is installed on a path of the sample tube between a sample tube supporting unit for supporting, during an NMR measurement, the sample tube used for the NMR measurement and an insertion port through which the sample tube is inserted in and extracted from the sample tube supporting unit. The direction shifting mechanism has a shape which partially includes a form of an arc, and the shape is designed to cause the sample tube to change its direction in such a manner that the sample tube is turned toward the insertion port along the arc while being maintained in contact with at least two points on an inner wall of the direction shifting mechanism.