A method of manufacturing an assembled shaft, comprising the following steps: - at least one of a step of expanding the inner diameter of at least a joining portion of a first shaft element and a step of reducing the outer diameter of at least a joining portion of a second shaft element; - positioning the joining portion of the first shaft element around the joining portion of the second shaft element; - welding the first shaft element and the second shaft element by forcing a current flow through the first shaft element and the second shaft element; and - at least one of a step of reducing the inner diameter of at least the joining portion of the first shaft element and a step of increasing the outer diameter of at least the joining portion of the second shaft element; - further comprising at least one of the following two steps: - forming a protrusion on the first shaft element that is directed to the second shaft element; and - forming a protrusion on the second shaft element that is directed to the first shaft element; and - further comprising the following step: - welding the first shaft element and the second shaft element by melting the protrusion by the current flow; - wherein the joining portion of the first shaft element is arranged around the joining portion of the second shaft element by press fit. - at least one of a step of expanding the inner diameter of at least a joining portion of a first shaft element and a step of reducing the outer diameter of at least a joining portion of a second shaft element; - positioning the joining portion of the first shaft element around the joining portion of the second shaft element; - welding the first shaft element and the second shaft element by forcing a current flow through the first shaft element and the second shaft element; and - at least one of a step of reducing the inner diameter of at least the joining portion of the first shaft element and a step of increasing the outer diameter of at least the joining portion of the second shaft element; - further comprising at least one of the following two steps: - forming a protrusion on the first shaft element that is directed to the second shaft element; and - forming a protrusion on the second shaft element that is directed to the first shaft element; and - further comprising the following step: - welding the first shaft element and the second shaft element by melting the protrusion by the current flow; - wherein the joining portion of the first shaft element is arranged around the joining portion of the second shaft element by press fit. - forming a protrusion on the first shaft element that is directed to the second shaft element; and - forming a protrusion on the second shaft element that is directed to the first shaft element; and - further comprising the following step: - welding the first shaft element and the second shaft element by melting the protrusion by the current flow; - wherein the joining portion of the first shaft element is arranged around the joining portion of the second shaft element by press fit. - welding the first shaft element and the second shaft element by melting the protrusion by the current flow; - wherein the joining portion of the first shaft element is arranged around the joining portion of the second shaft element by press fit.