Provided is a screw motion mechanism capable of facilitating connection of an axial end of a threaded shaft with respect to a structural body while preventing a rotation of the threaded shaft, and capable of preventing application of an excessive torque to a nut member and the threaded shaft and preventing damage on those members. The screw motion mechanism includes: a threaded shaft (30) having an outer peripheral surface provided with a helical thread groove, the threaded shaft (30) having at least one axial end coupled to a first structural body; a nut member (40) held in a rotatable manner with respect to a second structural body which is movable in an axial direction of the threaded shaft with respect to the first structural body, the nut member (40) being threadedly engaged with the threaded shaft; and a spherical joint (32) for coupling the at least one axial end of the threaded shaft (30) to the first structural body, the spherical joint (32) including: a spherical portion (33, 61); and a sphere receiving portion (36, 60) for housing the spherical portion. When assuming an axial force applied to the threaded shaft (30) as a variable, a line of a rotational torque intersects with a line of a sliding torque in a graph, and the sliding torque exceeds the rotational torque under an initial state in which the axial force is not applied to the threaded shaft (30).