Magnetic disk device

A magnetic disk device comprising:

• a base;
• five or more magnetic disks;
• a head actuator;
• and
• a spindle motor, wherein
• the base includes:
• a bottom wall having a second thickness;
• and
• a side wall being erect along a periphery of the bottom wall,
• the base accommodates the five or more magnetic disks,
• the head actuator includes a magnetic head supported in a freely movable manner,
• the spindle motor includes:
• a sleeve with a first hole, fixed to the bottom wall;
• a shaft inserted in the first hole in a freely rotatable state;
• and
• a hub that is freely rotatable together with the shaft, the hub including:
• a first part with a shaft opening into which an upper end of the shaft is inserted;
• a second part extending from an outer periphery of a lowermost surface of the first part in a first direction being from the magnetic disks toward the bottom wall;
• and
• a third part having a first thickness, facing the bottom wall, and extending from a lowermost surface of the second part in a second direction orthogonal to the first direction
• the first thickness of the third part is set such that a value obtained by dividing the second thickness by the first thickness is greater than or equal to 1.89.