A wedge tapping device for a rotating electrical machine, which is to be inserted through a gap between a rotor and a stator of the rotating electrical machine to tap a wedge of the rotating electrical machine, the wedge tapping device comprising: - a tapping portion, which is configured to tap the wedge of the rotating electrical machine, and includes a tapping force measuring instrument configured to measure a tapping force of the tapping; - an energy supplying portion configured to apply tapping energy to the tapping portion; - an absorbing portion configured to suppress energy to be applied to the tapping portion; and - a tapping arm, on which the tapping portion is disposed, and which has a longitudinal direction in a direction perpendicular to a direction in which the tapping portion performs tapping, - wherein the tapping arm is disposed so that the longitudinal direction is perpendicular to a circumferential direction of the rotor when the tapping is performed in the gap, and - wherein the tapping portion, the energy supplying portion, and the absorbing portion are disposed in parallel along the longitudinal direction of the tapping arm, - wherein the tapping portion is disposed at an end of the tapping arm, and wherein the tapping arm is supported so as to be rotatable about a fulcrum fixed to a main body, said main body being a casing of the wedge tapping device, wherein the energy supplying portion includes a tapping elastic body, which is configured to generate energy for rotating the tapping arm so that the tapping portion taps the wedge, characterized in that the wedge tapping device further comprises: a cam configured to rotate the tapping arm about the fulcrum; and a rotation driving portion configured to rotate the cam, wherein the rotation driving portion has a rotation axis oriented perpendicular to a pivot axis of the tapping arm, and wherein the cam has a diameter that is larger in a part in contact with the tapping arm when the tapping elastic body releases the energy than in a part in contact with the tapping arm when the tapping elastic body stores the energy. - a tapping portion, which is configured to tap the wedge of the rotating electrical machine, and includes a tapping force measuring instrument configured to measure a tapping force of the tapping; - an energy supplying portion configured to apply tapping energy to the tapping portion; - an absorbing portion configured to suppress energy to be applied to the tapping portion; and - a tapping arm, on which the tapping portion is disposed, and which has a longitudinal direction in a direction perpendicular to a direction in which the tapping portion performs tapping, - wherein the tapping arm is disposed so that the longitudinal direction is perpendicular to a circumferential direction of the rotor when the tapping is performed in the gap, and - wherein the tapping portion, the energy supplying portion, and the absorbing portion are disposed in parallel along the longitudinal direction of the tapping arm, - wherein the tapping portion is disposed at an end of the tapping arm, and wherein the tapping arm is supported so as to be rotatable about a fulcrum fixed to a main body, said main body being a casing of the wedge tapping device, wherein the energy supplying portion includes a tapping elastic body, which is configured to generate energy for rotating the tapping arm so that the tapping portion taps the wedge, characterized in that the wedge tapping device further comprises: a cam configured to rotate the tapping arm about the fulcrum; and a rotation driving portion configured to rotate the cam, wherein the rotation driving portion has a rotation axis oriented perpendicular to a pivot axis of the tapping arm, and wherein the cam has a diameter that is larger in a part in contact with the tapping arm when the tapping elastic body releases the energy than in a part in contact with the tapping arm when the tapping elastic body stores the energy. a cam configured to rotate the tapping arm about the fulcrum; and a rotation driving portion configured to rotate the cam, wherein the rotation driving portion has a rotation axis oriented perpendicular to a pivot axis of the tapping arm, and wherein the cam has a diameter that is larger in a part in contact with the tapping arm when the tapping elastic body releases the energy than in a part in contact with the tapping arm when the tapping elastic body stores the energy.