The invention provides an axial rotary torsion sensor comprising an idle wheel and a plurality of strip-shaped elastic sheets. The idle wheel is configured between a force inlet shaft and a force outlet shaft, which are respectively used as tangent line action force to drive the idle wheel to rotate along a circumference of a central axis. At least one of the elastic sheets is provided with a strain gauge, and one end part of the elastic sheet is fixed, and the other end is used to absorb the counter-acting force carried by the idle wheel, and the strain gauge is used to sense the bending deformation to generate strain to be used as a torsion sensing value between the force inlet shaft and the force outlet shaft. The above mentioned elastic sheet is parallel to the axial direction of the force inlet shaft, and the problems of the conventional torsion sensors such as low sensing accuracy, insufficient sensitivity, and inability of shrinkage of radial volume are solved.