An object of the invention is to provide a method of assembling a disc which can reduce an unbalance of a rotating portion. The method of assembling a disc-like recording medium has a first step of mounting a disc-like recording medium to a disc apparatus in a state capable of moving the disc-like recording medium with respect to a hub of a spindle motor in a direction of a disc radius, a second step of pressing an outer diameter of the disc in a direction of a center axis of the hub by a first flat member so as to bring an inner diameter of the disc into contact with an outer diameter of a rotary axis of the hub, a third step of pressing back the outer diameter of the disc contact with the first flat member and the outer diameter of the disc at an opposite position to the center of the disc in an inverse direction to a pressing direction of the first flat member to a half of an amount of tolerance between the inner diameter of the disc and the outer diameter of the hub, by a second flat member placed substantially in parallel to the first flat member and in an opposite side to the center axis of the hub, and a fourth step of fixing the disc to the spindle motor hub by a clamp member.