An energy conversion apparatus for executing conversion from one to another of electrical energy and mechanical energy, comprising: a magnet ring (2, 3, 4), a direction of central axis of which is vertical, the magnet ring including: a ring-shaped magnet holder in which a plurality of magnet boxes an upper part of which is opened, is formed; at least one permanent magnet that is housed in each of the plurality of magnet boxes of the magnet holder, each of the at least one permanent magnet being magnetized along a circumferential direction of the magnet holder; a cover that is formed in a ring shape having a width wider than that of the magnet holder, and that is attached to an upper surface of the magnet holder so as to have the same center as that of the magnet holder, and that has an extension part extending in a radial direction of the magnet holder from the magnet holder; a gear that is fixed onto the cover and the magnet holder so as to have the same center as those of the magnet holder and the cover, and each of the at least one adjacent permanent magnet is arranged in such a manner that opposite polarities face each other in a corresponding magnet box of the magnet holder, in case that the number of the at least one permanent magnet is plural; the energy conversion apparatus further comprising: a ring-shaped case, a central axis of which is common with the central axis of the magnet ring, that houses the magnet ring (2, 3, 4) and in which a window part for exposing part of the gear to an outside is formed; a plurality of wheels that are arranged between an internal surface of the case and the magnet holder so as to be contacted with a bottom surface of the case and the extension part of the cover; a defining member through which each axis of rotation of the plurality of wheels is passed and that defines a relative distance between the plurality of wheels; and at least one coil that is wound around the case. a magnet ring (2, 3, 4), a direction of central axis of which is vertical, the magnet ring including: a ring-shaped magnet holder in which a plurality of magnet boxes an upper part of which is opened, is formed; at least one permanent magnet that is housed in each of the plurality of magnet boxes of the magnet holder, each of the at least one permanent magnet being magnetized along a circumferential direction of the magnet holder; a cover that is formed in a ring shape having a width wider than that of the magnet holder, and that is attached to an upper surface of the magnet holder so as to have the same center as that of the magnet holder, and that has an extension part extending in a radial direction of the magnet holder from the magnet holder; a gear that is fixed onto the cover and the magnet holder so as to have the same center as those of the magnet holder and the cover, and each of the at least one adjacent permanent magnet is arranged in such a manner that opposite polarities face each other in a corresponding magnet box of the magnet holder, in case that the number of the at least one permanent magnet is plural; a ring-shaped magnet holder in which a plurality of magnet boxes an upper part of which is opened, is formed; at least one permanent magnet that is housed in each of the plurality of magnet boxes of the magnet holder, each of the at least one permanent magnet being magnetized along a circumferential direction of the magnet holder; a cover that is formed in a ring shape having a width wider than that of the magnet holder, and that is attached to an upper surface of the magnet holder so as to have the same center as that of the magnet holder, and that has an extension part extending in a radial direction of the magnet holder from the magnet holder; a gear that is fixed onto the cover and the magnet holder so as to have the same center as those of the magnet holder and the cover, and each of the at least one adjacent permanent magnet is arranged in such a manner that opposite polarities face each other in a corresponding magnet box of the magnet holder, in case that the number of the at least one permanent magnet is plural; the energy conversion apparatus further comprising: a ring-shaped case, a central axis of which is common with the central axis of the magnet ring, that houses the magnet ring (2, 3, 4) and in which a window part for exposing part of the gear to an outside is formed; a plurality of wheels that are arranged between an internal surface of the case and the magnet holder so as to be contacted with a bottom surface of the case and the extension part of the cover; a defining member through which each axis of rotation of the plurality of wheels is passed and that defines a relative distance between the plurality of wheels; and at least one coil that is wound around the case. a ring-shaped case, a central axis of which is common with the central axis of the magnet ring, that houses the magnet ring (2, 3, 4) and in which a window part for exposing part of the gear to an outside is formed; a plurality of wheels that are arranged between an internal surface of the case and the magnet holder so as to be contacted with a bottom surface of the case and the extension part of the cover; a defining member through which each axis of rotation of the plurality of wheels is passed and that defines a relative distance between the plurality of wheels; and at least one coil that is wound around the case.