Pivot device and portable device

The utility model provides a pivot device and a portable device adopting the same. The pivot device comprises a concave locating plate and a convex locating plate, which perform rotation oppositely, wherein a first locating groove, a second locating groove and a first locating lug are arranged on the concave locating plate; and a second locating lug and a third locating lug are arranged on the convex locating plate. When an upper cover of the portable device is closed, the second locating lug is embedded in the first locating groove to provide a first peak torsion force; when the upper cover is opened, the second locating lug is separated from the first locating groove, and slides on the surface of the concave locating plate to provide a common torsion force; and when the upper cover is opened continuously, the third locating lug is propped against the first locating lug to provide a second peak torsion force, and the first locating lug is forced to go away from the surface of the concave locating plate at th