A crank driving apparatus, including a first supporting member having an insertion hole, into which a driving shaft is inserted, and attached to the driving shaft via the insertion hole so as to be unrotatable relative to the driving shaft, a second supporting member including an eccentric shaft and attached to the first supporting member so as to be unrotatable relative to the first supporting member, and a coupling member rotatably supported by the second supporting member via the eccentric shaft and coupled to an object that is to be driven, wherein the second supporting member is disposed in such a manner that an attachment position of the second supporting member relative to the first supporting member is adjustable in an eccentric direction in which an axis of the eccentric shaft is positioned eccentric to an axis of the driving shaft, wherein the attachment position of the second supporting member relative to the first supporting member in the eccentric direction determines an eccentric distance of the axis of the eccentric shaft from the axis of the driving shaft, and wherein an amount of drive of the crank driving apparatus is changed by changing the eccentric distance as a result of changing the attachment position, the crank driving apparatus comprising: three or more first eccentric-distance index portions (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) disposed on one of the first supporting member and the second supporting member at different positions in the eccentric direction; and a second eccentric-distance index portion (X, Y; S, T) disposed on the other one of the first supporting member and the second supporting member so that a position of the second supporting member is allowed to coincide with positions of the first eccentric-distance index portions in the eccentric direction on the one supporting member, wherein each of the first eccentric-distance index portions (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) and the second eccentric-distance index portion (X, Y; S, T) is formed at a distance, from the center of the insertion hole or the axis of the eccentric shaft, at which the eccentric distance is fixed at a predetermined eccentric distance determined in advance for each of the first eccentric-distance index portions (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) when the positions of the respective first eccentric-distance index portion (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) and the second eccentric-distance index portion (X, Y; S, T) coincide with each other in the eccentric direction, characterized in that the second eccentric-distance index portion is an end face (X, Y; S, T) of the other supporting member and the end face (X, Y; S, T) extends in a direction perpendicular to the eccentric direction, wherein the three or more first eccentric-distance index portions are end faces (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) of the one supporting member disposed so as to correspond to the second eccentric-distance index portion (X, Y; S, T) and each end face (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) is formed on the one supporting member so as to extend in a direction parallel to the end face forming the second eccentric-distance index portion. three or more first eccentric-distance index portions (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) disposed on one of the first supporting member and the second supporting member at different positions in the eccentric direction; and a second eccentric-distance index portion (X, Y; S, T) disposed on the other one of the first supporting member and the second supporting member so that a position of the second supporting member is allowed to coincide with positions of the first eccentric-distance index portions in the eccentric direction on the one supporting member, wherein each of the first eccentric-distance index portions (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) and the second eccentric-distance index portion (X, Y; S, T) is formed at a distance, from the center of the insertion hole or the axis of the eccentric shaft, at which the eccentric distance is fixed at a predetermined eccentric distance determined in advance for each of the first eccentric-distance index portions (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) when the positions of the respective first eccentric-distance index portion (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) and the second eccentric-distance index portion (X, Y; S, T) coincide with each other in the eccentric direction, characterized in that the second eccentric-distance index portion is an end face (X, Y; S, T) of the other supporting member and the end face (X, Y; S, T) extends in a direction perpendicular to the eccentric direction, wherein the three or more first eccentric-distance index portions are end faces (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) of the one supporting member disposed so as to correspond to the second eccentric-distance index portion (X, Y; S, T) and each end face (a1, a2, b1, b2, A, B; m1, m2, n1, n2, M, N) is formed on the one supporting member so as to extend in a direction parallel to the end face forming the second eccentric-distance index portion.