There is provided a motor allowing for an increase in the rigidity of a hydrodynamic bearing by controlling a gap between a shaft and a sleeve as well as minimizing power consumption and a recording disk derive device including the motor. The motor includes a sleeve having a cylindrical shape and including a hole whose inner circumferential surface has at least one dynamic pressure groove therein; and a shaft rotatably inserted into the hole of the sleeve and having at least one rigidity reinforcing portion protruding in an outer diameter direction from an outer circumferential surface thereof corresponding to the dynamic pressure groove.