To provide a portable key in which operability is improved when opening and closing a key.

A portable key includes: a grip part; and a key provided with a base end in the grip part via a support shaft, and protruding from a storage position where the key is stored in the grip part to rotate to a use position where the key is brought into an approximately horizontal state to the grip part. A mechanism storage part is formed in one end of the grip part. A cam member configuring a torque mechanism and a drive spring are assembled in the mechanism storage part with the support shaft. On the way of rotating the key to the use position by raising or pulling out with fingers, a torque of the torque mechanism is reversed via the respective uneven cam surfaces of the cam member. Thereafter, the key is rotated to the use position by a spring force of the drive spring.