An impact buffer having a high buffering effect includes two or more impact buffering members with different hardness, contacted with at least one surface of a side surface part of an HDD unit positioned orthogonally to the rotation surface of a magnetic disk of the HDD unit, supports the HDD unit, buffers an impact applied to the HDD unit by expansion and contraction, further moderates the rotation of the HDD unit in the direction causing a head arm to move onto the disk at rest, prevents the head detachment, and can overcome the weaknesses of the head arm and an inertial latch structure.