A flywheel power storage system for storing supplied electric power in the form of rotational kinetic energy, comprising: a main shaft extending in a certain direction; a pair of rotary bodies attached to the main shaft, the rotary bodies counter rotating about the main shaft; a drive unit configured to synchronize rotation periods of the rotary bodies rotating about the main shaft with each other; and a stator with both end portions each having the main shaft attached thereto, the main shaft outwardly extending from each of the end portions, the stator being made of a magnetic material, wherein each of the rotary bodies is made of a magnetic material and has a substantially disk shape extending radially from the main shaft in a direction perpendicular to the main shaft, and the rotary bodies are disposed with the stator therebetween, and wherein the drive unit includes a pair of exciting coils each disposed on one of the end portions, the main shaft passes through center core portions of the exciting coils, and the exciting coils cause the rotary bodies to generate a rotation force based on a magnetic resistance between the stator and each of the rotary bodies when being excited by input and output of the electric power to and from the flywheel power storage system, characterized in that the stator has a plurality of through-holes that pass therethrough in a direction in which the main shaft extends and that are arranged on a circumference of a circle having the center at the main shaft and a predetermined radius with a spacing therebetween in the circumferential direction, and each of the rotary bodies has a facing surface that faces the stator and a plurality of protrusions (37, 38) that protrude, toward the stator, from the facing surface on the circumference of the circle having the predetermined radius at positions corresponding to the through-holes. a main shaft extending in a certain direction; a pair of rotary bodies attached to the main shaft, the rotary bodies counter rotating about the main shaft; a drive unit configured to synchronize rotation periods of the rotary bodies rotating about the main shaft with each other; and a stator with both end portions each having the main shaft attached thereto, the main shaft outwardly extending from each of the end portions, the stator being made of a magnetic material, wherein each of the rotary bodies is made of a magnetic material and has a substantially disk shape extending radially from the main shaft in a direction perpendicular to the main shaft, and the rotary bodies are disposed with the stator therebetween, and wherein the drive unit includes a pair of exciting coils each disposed on one of the end portions, the main shaft passes through center core portions of the exciting coils, and the exciting coils cause the rotary bodies to generate a rotation force based on a magnetic resistance between the stator and each of the rotary bodies when being excited by input and output of the electric power to and from the flywheel power storage system, characterized in that the stator has a plurality of through-holes that pass therethrough in a direction in which the main shaft extends and that are arranged on a circumference of a circle having the center at the main shaft and a predetermined radius with a spacing therebetween in the circumferential direction, and each of the rotary bodies has a facing surface that faces the stator and a plurality of protrusions (37, 38) that protrude, toward the stator, from the facing surface on the circumference of the circle having the predetermined radius at positions corresponding to the through-holes.