A magnetostrictive unit (10a, 60a) for a magnetostrictive sensor (10, 60) comprising: a columnar or tubular substrate (12, 62); and a plating film (14, 64) made of a magnetostrictive material and disposed on an outer peripheral surface of the substrate (12, 62), characterized in that the substrate (12, 62) includes a first base portion (24, 72), a second base portion (20, 28, 68), and a tilt portion (22, 26, 70, 74) disposed between the first base portion (24, 72) and the second base portion (20, 28, 68) in an axial direction of the substrate (12, 62) and connecting the first base portion (24, 72) and the second base portion (20, 28, 68), the first base portion (24, 72) has an outer peripheral surface (24a, 72a) parallel to a shaft center of the substrate (12, 62) in a cross-section including the shaft center and extending in the axial direction of the substrate (12, 62), the tilt portion (22, 26, 70, 74) has an outer peripheral surface being a slope (22a, 26a, 70a, 74a) tilted relative to the shaft center in the cross-section, the plating film (14, 64) is formed on the outer peripheral surface (24a, 72a) of the first base portion (24, 72) and on the slope (22a, 26a, 70a, 74a) in such a manner that one end of the plating film (14, 64) in the axial direction is located on the slope, and the plating film (14, 64) has a thickness on the slope (22a, 26a, 70a, 74a) smaller than a thickness of the plating film (14, 64) on the outer peripheral surface (24a, 72a) of the first base portion (24, 72), the first base portion has a diameter smaller than the diameter of the second base portion (20, 28), and the plating film is formed such that a surface of the plating film is recessed with respect to an outer peripheral surface (20a, 28a) of the second base portion (20, 28), or the first base portion has a diameter larger than the diameter of the second base portion (28, 68). a columnar or tubular substrate (12, 62); and a plating film (14, 64) made of a magnetostrictive material and disposed on an outer peripheral surface of the substrate (12, 62), characterized in that the substrate (12, 62) includes a first base portion (24, 72), a second base portion (20, 28, 68), and a tilt portion (22, 26, 70, 74) disposed between the first base portion (24, 72) and the second base portion (20, 28, 68) in an axial direction of the substrate (12, 62) and connecting the first base portion (24, 72) and the second base portion (20, 28, 68), the first base portion (24, 72) has an outer peripheral surface (24a, 72a) parallel to a shaft center of the substrate (12, 62) in a cross-section including the shaft center and extending in the axial direction of the substrate (12, 62), the tilt portion (22, 26, 70, 74) has an outer peripheral surface being a slope (22a, 26a, 70a, 74a) tilted relative to the shaft center in the cross-section, the plating film (14, 64) is formed on the outer peripheral surface (24a, 72a) of the first base portion (24, 72) and on the slope (22a, 26a, 70a, 74a) in such a manner that one end of the plating film (14, 64) in the axial direction is located on the slope, and the plating film (14, 64) has a thickness on the slope (22a, 26a, 70a, 74a) smaller than a thickness of the plating film (14, 64) on the outer peripheral surface (24a, 72a) of the first base portion (24, 72), the first base portion has a diameter smaller than the diameter of the second base portion (20, 28), and the plating film is formed such that a surface of the plating film is recessed with respect to an outer peripheral surface (20a, 28a) of the second base portion (20, 28), or the first base portion has a diameter larger than the diameter of the second base portion (28, 68).